Have you jailbreaked and unlocked your iPhone? If you have, you can buy a SIM card over in Europe and use your phone to make calls, send texts, check email, etc. However, if your phone is not unlocked, then it probably would be best to leave your phone on airplane mode, and pick up any free wifi hotspot to use for Skype and/or Google Voice to keep in touch back home. Whatever you do, do not get an AT&T international voice/data plan. You will run up quite a lengthy bill.