Internet And Phone Options

Yes, you can just buy a SIM card for your phone when you get to Europe. But your phone must be unlocked, and it needs to have the radio frequencies required to work in Europe (Europe uses different radio frequencies than are used in say North America.) If you have a flip phone, it is less likely to work. (What's the exact make/model?) If you have a smart phone, more likely to work - they tend to support international use better than the old flip phones did. Still must be unlocked either way.

If you buy a SIM over there, you'll temporarily have an Irish or British phone number. Prepaid SIM cards may or may not come with international minutes you can use to call overseas from Ireland or the UK. If you have a smart phone, you can install the Google Hangouts app (and also Hangouts Dialer app if you have an Android) and make free voice calls to the US (if you are American), even to landlines. Hangouts works on WiFI too and doesn't even need a SIM card or mobile service to work, as long as you have WiFi. If you aren't from the US, then Hangouts isn't going to be free to make calls with.

Who is your phone provider?
We are on Sprint and their plans come with Free Text and 2G Data speeds at no cost.
When we land we get the "Welcome to England" text and it's already activated.
Calls are 20 cents a minute if you need to call someone.
I would call your provider and tell them what you're doing and they may have a plan you can get for the time you're there.

Definitely talk to your phone provider. Either get some coverage through them (won't be a bargain but it might not be too exorbitant for what you need to use the phone for) - or if you want to get a SIM card in England and Ireland, make sure your phone is unlocked. Also, that's very good advice about being sure the phone has the right frequency band to operate in Europe.

If your phone is unlocked and will work in England and Ireland, and you want to get a SIM card, after you check into your hotel, find a store like the ones for Three (3), one of the big mobile phone carriers. They'll sell you one and set it up for you. Been there, done that. You'll end up with a UK phone number which you can give to your family, and probably plenty of minutes you can use to make calls to the US.

I have att and my phone is a samsung note 5.
I will go to the att store tomorrow and ask about band freq. Thank you so much

We used the ATT $10/day plan on our last trip. We only needed to call home a couple of times so only paid for those days. You can use wifi to send emails without turning on the cellular service (leaving phone in airplane mode, for example.) Since changing SIM will change your phone number to a local UK number, this can be confusing to the folks trying to call you and you won't get calls or texts from people to whom you did not provide the new number.

Stan's point is important.

If your goal is to be able to call your family, Andrew has laid out some ways to do this cheaply, and he can give you lots of details if you need them. However, if your goal is for your family to be able to reach you, and they aren't tech-friendly either, you'll probably want to keep your AT&T SIM in your phone, and use one of their options. It will cost more, but then your phone number won't change; people will reach you as they do now, just by calling or texting your current number. It's also easy for you, because when using your AT&T phone in Europe, you just pretend you're still in the US. In other words, to call an Irish number from your AT&T phone, you dial +353, then area code (dropping the initial 0), then the number. To call an English number from your AT&T phone, you dial +44, then the area code (dropping the initial 0), then the number. To call a US number, just dial it as you do in the US (area code plus number).

You can certainly be reached on a Irish or English mobile phone number from the US. But, you do have to find a way to get the number to your family (I e-mail and text it), and they have to understand how to call or text this number from their phones in the US, and they have to be willing to pay for the calls and texts (which, depending on their plan, can be affordable or expensive).

I’m with ATT, when I go to England I purchase one of their international plans. I use World Connect, unlimited texting and .08 cents calling land line, 28 cents calling another cell phone, and of course FaceTime is free.

If you use Hangouts as I described above, you can make free calls home to the US, but you can't automatically get incoming calls too - unless you also sign up with Google Voice, which will give you a (free) US phone number as well, which can "ring" in Hangouts for incoming calls. Then you can give your relatives at home a US phone number they can call for free, and you won't have to give them a UK or Irish phone number that is an international call for them.

Or, just check your AT&T voicemail occasionally by calling your own number (free, with Hangouts) and if someone has left you a voicemail, call them back with Hangouts. Or tell people to email you if they want a call back.

I am not technically phone friendly.

I had that ^^ in mind when I posted above. I mentioned what I think is the best way for someone who's not very tech-y to get a UK SIM Card (have the person in the store set it up for you), but I also mentioned, and want to underline, that the best option in this case is probably some coverage by AT&T for the trip instead of messing with a UK SIM card. Good to hear from AT&T customers that they've found reasonable plans for that. (And I had that in mind when deciding not to mention the Google Voice/Hangouts thing.)

I am pretty tech-y and have in the past bought SIM cards for my unlocked US phone while in the UK. And the bit about having a UK phone number was a bit of a PITA, though not a deal-breaker. Now I have a mobile provider (Project Fi) that works internationally, and I really like not having to fiddle with SIM cards and not having a new/temporary phone number. Sweet!