Which Pre-Paid data SIM card?

What is your service provider at home?
T-mobile has an excellent plan for I think $50 a month (I think it's called Simple Choice) which includes international data roaming to many countries including Italy. Check at one of their stores or inquire by phone/online.

Definitely look at options offered by the current carrier. They have become somewhat reasonable over the past few years. As long as one remembers to use WIFI when possible (at the hotel, in restaurants) and no streaming of video unless on WIFI, you usually do not run the risk of outlandish bills. Offline maps save on GB usage too.

That said, if she can pop into a WIND, TIM or Vodaphone store, it only takes 10 minutes to get set up with a new SIM, unless there's a crowd.

What is their first stop?

It would help to know which cellular network your daughter is using at home, as that may be the easiest and least expensive method. If that's not an option, you could look at any of the "travel phone" firms such as Cellular Abroad, Mobal, EuroBuzz or iRoam. One of the advantages of using these rather than a local plan is that service is post-paid (calls charged to a credit card), so there's no need to top-up.

In order to minimize usage of cellular data, your daughter can also use free Wi-Fi that's provided most places in Italy these days. I tend to leave the data roaming turned "off" unless I need it. It would best to use Wi-Fi for data intensive functions such as uploading photos.

Existing carrier is not an option; we use a T-Mobile MNVO under pay-as-you-go plans (saves us hundreds of dollars/year over the expensive monthly plans, as none of us use voice or data much as WiFi in our area is everywhere, and texts are 2-cents - even the teenager is doing under $15/month, her parents considerably less). This MNVO has no overseas roaming options. I understand it is relatively painless to purchase SIM cards locally, and if I were traveling that's exactly what I'd do, but this is her first time overseas and she's nervous enough without adding one more thing to the mix.

Everything I've read suggests WiFi access in Italy is spotty at best, and horrific at worst, so while she's smart enough to use it if she can connect to it, I'm reluctant to depend on it. As to not using cellular to upload photos, I understand the bandwidth involved - been involved in network design since the late 1980's, and specifically bought her the phone she has because of the 13MP rear camera, so yeah, it's gonna hurt. On the other hand, should her phone be stolen or lost, uploading to my Copy cloud storage account at the time of creation will save valuable memories up to the point of phone loss, instead of the night or even days before, so I'm perfectly willing to swallow the money to cover the security. She's a smart kid, so she'll use WiFi whenever possible, but after what I've read it worries me to depend on it. I guess it's silly, but I want to have as much as possible handled before she arrives, so she can spend the entire trip having fun instead of dealing with the practical crap we have to handle every other day of our lives.

My fear is spending stupid amounts on a SIM card and having her get there with a card that doesn't connect, trying to trouble-shoot herself when she should be picking up gelatto in her limited spare time. (D*mned kid doesn't like coffee...traveling to the heart of espresso, and passing on it. Breaks my heart. ;)

First day arrive in Milan, drive to Verona, then on to Venice for dinner and overnight, clearly running on adrenalin by the end of that long travel day - rest of the tour is similar with the exception of two nights in Florence and two nights in Rome. Typical rushed tour, with a tour agency that has been no help whatsoever in planning...once they got the payment, participants are on their own - none of the planning meetings they promised in their sales pitch (not even discussions about the optional side-tours they promised!), no information about the simple things like weight restrictions, etc. (yes, some info is readily available, but geez). I'll never recommend this "student tour" outfit to anyone. But that's a different rant that doesn't belong here...

I wish you best of luck. Before we went to Italy in December, I wanted to get a SIM card before we left. Trying to find a decent company was the hardest and most frustrating part of planning the trip. I eventually gave up. Right before we left, our provider, Verizon, offered a new international calling plan and we signed up for it. We never used it.

Wi-Fi in Italy is becoming more widespread and reliable. We were able to do everything we wanted using Wi-Fi, that's why we didn't use our phone plan.

If you do find a prepaid SIM with reasonable rates, make sure you share the info to help others. I hope your daughter has a wonderful trip. I took a school trip back in 1966. There was this cute 14 year old girl who was part of our group. That cute girl and I just returned from celebrating our first kiss, which we shared in Florence on August 10, 1966.

Why even need the SIM card if it sounds like most stuff Skype and Uploading photos will be done on WIFI. Keep the phone in airplane mode and just look for a shop that has WIFI. Order a caffee or pastry, enjoy it and upload the photos from the shop.

DougMac: Best. Story. Ever. Congrats to you both!

Some research from the past few days, hopefully without breaking any posting guidelines:

Mobal: 0.39/M, ~$400/G (Yipe!)

iRome: Hard to get accurate numbers, looks like 0.39/M but not sure. Not trusing any company that obscures information.

EuroBuzz: $50/month, free 16 KB/sec (2g) data (same as T-Mobile's International Roaming), 3g apparently not available. (Nice price, but at that data rate, a single 4MB photo would take between 4.5 and 5 minutes to upload. Surprisingly good reviews around the Net, though.)

Cellular Abroad: $60 for SIM card, additional $40 for 1G data

Telestial: $49 for SIM, 1G included, additional from 10-euros/G, requires pre-reg with passport

Telestial: International Roaming SIM 1G 3g data $99, company reviews mixed-to-negative on Amazon

HolidayPhone: $61.90 for 10G 3g data-only SIM - reviews mixed, Facebook page contains rants

Best price is clearly HolidayPhone and 10G should be overkill for the trip, but I worry about all the complaints on their Facebook page...I don't want the kid to have to troubleshoot the phone while she's jet-lagged. Does anyone have any direct experience with this one?

I am comforted that WiFi is reported as being more reliable in Italy than Internet articles would imply...if the hotels have reasonable connections, she can Skype to the grandparents from there freeing mobile data for other things.

I don't know where you read that wifi in Italy is spotty. I have yet to find a hotel in the cities you mentioned that doesn't have one. The nominal speed from Italian providers is 7 Mbps or 20 Mbps depending on the contract. However the actual average speed tends to be around 5 Mbps and 7 Mbps respectively. Those averages are still higher than you get from many American providers.
Also those are national averages as big cities have fiber optic networks, which are substantially faster, and your daughter seems to be headed to large cities.
The only issue might be if your daughter's hotel room is far from the router (many small hotels just put one router per floor), as Italian buildings are all reinforced concrete and old buildings also have very thick walls. In that case all she needs to do, is ask the hotel manager to tell her where the best reception of the signal is.
So in that respect she won't need a lot of data, since I imagine she would upload the pictures at the end of the day in her hotel, not necessarily in the streets, however that is possible too. Florence has now free wifi hot spots (530 of them) covering the city center (courtesy of the City). They allow you a daily limit of 2 hours of free navigation for a max of 300 Mbs, but that is enough. Not sure how speedy that is.
Many bars/restaurants have that too for their customers.
Venice has also the same. I've used it, but given the maze of small alleys, it was good only in larger piazzas.
Buying a local plan is easy. Just enter a Vodafone or Tim store, and they'll give you 2 Gb/300min/300txt worldwide for 30 euro. But you still need to have a GSM smart phone that works in Europe.
Having said this it's convenient to have a smart phone that you can use freely like at home, but it's not essential for her purposes. She can wait to do the heavy stuff when she's back in the hotel, unless she wants to upload in the street in the City provided wi-fi or in a bar with good wifi.

Look into a KnowRoaming SIM. It's actually a sticker that goes on your regular SIM; you choose whether you are using your regular SIM or the KnowRoaming SIM via an app on the phone (which must be unlocked). Their rates are lower than the other international SIMs you mentioned, and my friend tried it in Italy last year and it worked well.

Details here: https://www.knowroaming.com/

As long as she's staying in Italy try Witourist.com me and my wife have used them the last 2 years we have been there and it works well. My daughter is studying abroad in March for 8 weeks and I am getting this for her. This gives you Personel wifi for her phone and she can use data as if it's on a regular wifi network. She can FaceTime from anywhere to you back in the states for no data charges. Good luck

I want to thank everyone who has responded, but I think I need to mention one more time that she will not have the time to enter a local store and pick up a SIM card there...as I mentioned in a previous post, if I were traveling that is what I would do, but I'm not. I want to take all the hassle from her, and I want her phone to "just work" from the moment the plane lands.

I like portable hotspots (I have a phone that is used solely as a hotspot for my tablets and laptop)...but in this case I think it's an unnecessary layer, as she isn't taking any other computing device but her phone.

I started to dismiss out-of-hand the KnowRoaming since I intentionally bought her a dual-SIM phone, so why bother with an adhesive circuit board? But the more I think $8/day for unlimited data, the more embarrassed I am about closing my mind to it. I will read through the company website tomorrow when I'm fresh and alert and report back afterwards.

Off-topic, but my criteria for a phone to send with her were: inexpensive so I wouldn't cry if lost or stolen, dual-SIM, excellent camera, Android OS. Ended up buying her a BLU Life One 4G at the introductory $99. When it came in I played around setting it up, and...er...liked it so much I kept it and bought her another one. Been using that as my primary phone, and she'll have hers with her in Italy. The camera takes amazing pics and 720p video. It's short on memory, but I'm pretty good with Android and can use tools like Link2SD to write my own soft links to work around that.

How about Cellular Abroad's unlimited data-only plan? Should be worry-free.

I used them for a simple phone on a trip several years ago and the service was excellent.

As usual, running wildly late...

Looked into KnowRoaming, and as usual, "unlimited" it ain't - the fine print notes that the first 250M/day is guaranteed to be at 3g speeds, then they reserve the right to limit the user to edge speeds, or close down the connection completely. Also, while the Android app is available on the Play Store, it has to be manually emailed to anyone without a Play Store account - I did communicate with Customer Support on this issue, and they did reply promptly (although they use Google for their email provider, which is of course a privacy violation).

Still, I need to make a decision now, and while Cellular Abroad's unlimited data-only plan is reasonable, it too isn't "unlimited" (10G/month), and requires "renting" the SIM card (rending a 10-cent piece of plastic and circuit seems an unnecessary complication). The KnowRoaming is $30 to buy the sticker-circuit (includes a $10 credit voucher, so effectively $20) and $7/day for data - she will also be able to make voice calls if there's an emergency, otherwise can use WiFi and Skype to keep in touch. We should be able to monitor and refill the card via the Web interface, although I can't verify that until I buy the sticker. I'm hoping that, if WiFi is as prevalent as y'all have noted (remembering that she can't just "wander" into a cafe, at least during the day, as their days are heavily structured) that that 250M will be enough to store photos as they are taken - again, I do not want her to wait until evening to sync to Copy, since if the camera is lost or stolen during the day everything that day would be lost if she waited - syncing via 3g is more expensive, but much safer in a disaster.

After the trip is over, I'll report back on how well this thing works, noting any problems that arise.

If you know at which hotels your daughter is staying, google or see tripadvisors for reviews of the wifi quality. We found the hotel wifi quality to be excellent on our trip. We did most of our ccommunications in the evenings in Italy while at the hotel and people were awake at home. You really need to sit down in one place with a stable signal to upload lots of photos. (Even with LTE or 3G, you can lose signal if you are on the move). We also found lots of hotspots during the day.

I also purchased a local SIM from a TIM dealer for my phone which provided 30 days of 200 min international/local calls and 2 GB data for about 30 euros. The nice thing is that there are dealers everywhere to help get set it up and to fix problems. Mine worked flawlessly. On the other hand, my wife bought an international text package for her phone from our home carrier. It worked for a few days and then stopped working. There was no way to fix it.

EDIT: I googled Cellular Abroad. For Italy, it looks like CA is just a reseller for TIM and they have to mail you a TIM sim and you have to mail it back after the trip. Buying directly from TIM in Italy is way easier and cheaper and gives your daughter immediate local support.
KnowRoaming sounds quite nifty. But it sounds like setup can be tricky and may need some tweaking when you get into the country. Is your daughter tech savvy? And speeds may slow down. Remember that these service can on piggyback on to the local service.. Chances are KR will be using TIM which is one of the largest prviders in Italy.

Once again the local SIM option Is cheapest. The dealers deal with tourist all of the time.

Once again the local SIM option Is cheapest. The dealers deal with tourist all of the time.

Yes, I know, but as I have been saying, this is a structured school trip where her time is heavily scheduled with little time to be futzing around on her own, and I didn't want her having to either separate from the group to find a dealer, or just generally waste any of her time doing this. I want something that works from the moment the plane lands, not send her off to some dealer in a country where she doesn't speak the language (she's fifth-year Latin, which isn't much help anywhere on the planet) to buy something that in-country requires her to provide her passport, etc..

If I were going, or she were going with the family, this wouldn't be an issue. But I do not want her wasting valuable time hunting around for a SIM card. That was the entire purpose of the exercise - to have everything prepared for her before she leaves so her phone, "just works" - one less thing for her to worry about.

I'll wait until this is all over to make a full report, but I will say I was able, with careful web searches, to bring the price of the KnowRoaming board down to effectively nothing, saving that initial $20. (Total cost was $14.99, with $15 in usage credits.) I also acquired the Android app without using the Play Store, although that took more work.

there is a staffed Vodafone booth right there in baggage claim at Milan/MXP