I will be traveling to Milan with my teenage daughters and will be staying there for a month. We leave in a couple of weeks. I wanted to know if it was possible to buy a sim car here in Los Angeles before I leave instead of trying to figure out where to buy one there. I am also concerned about the language barrier and any confusion about the plan I am buying. Also, does anyone recommend one carrier over another. I would appreciate any advice on this. Thanks!
You can't buy an Italian SIM card until you get to Italy - you need to have your passport copied at the mobile store to activate the SIM. They have mobile stores like we have in the US. One of the most well known companies is called TIM. Another is Vodafone. Another is Wind.
You can just got to a store and do it in about an hour. All of these companies now have "tourist SIM cards" designed for visitors to Italy - for maybe about 30 Euros. These include mobile data and even some minutes can use to call the US.
Another option you'd have is to buy a SIM card from another European country (with different rules about needing to show your passport to buy it). I recently bought a Dutch Vodafone SIM card on eBay, no requirement to activate with my passport (I didn't even visit the Netherlands), got it two weeks later in the US, activated the SIM in my phone in the US, then had a working phone when I landed in Venice. I used the phone in Italy, Slovenia, and France without issue - free data roaming on Vodafone NL in Europe. (In a few weeks, all EU roaming is supposed to become free.) I got a package of 3GB of data for 20 Euros for a month (and $7 USD to buy the SIM card on eBay). It worked great for me. However, I needed the phone for data - I didn't make any calls to people in Italy. If you will be doing that, you'll probably want to wait until you get to Italy, so you can get an Italian SIM with an Italian phone number, so locals can call you for free.
Another option would be to switch to T-Mobile or Sprint before you leave for Italy (I assume you are not already with them). They both have free unlimited roaming data overseas (2G speeds only but probably good enough), plus 20 cents/minute for local calls or calls to the US. This also assumes you have a phone that works in Europe - most smart phones do, but older flip phones may not.
If you have a smart phone, no matter what option you choose for a SIM, you can use Google Hangouts to make free phone calls back to the US (on WiFi or using mobile data), even to landlines. You can call Italy, too, with Hangouts (say from WiFi, when you have a phone with no SIM card at all so no phone service)., but calls to Italy aren't free with Hangouts. You'd have to buy credit from Google and pay a few cents per minute per call.
Here's a good reference for SIM cards in Italy: