I can tell you about France. My wife and I go over there. Are you going to Paris?
The three major wireless carriers are Orange, SFR and Bouygues. They have shops all over France. You can get refill cards at any Tabac shop. We always pickup a local SIM card while we are there. Most hotels will have WiFi (Most WiFi restricts VOIP like Skype). If you want data on your phone, call it "internet", not data.
I have my AT&T account setup so I get email notification for voicemail, so I know when I have voicemail on my U.S. number. It's like 0.45 cents a minute to call the U.S. from France on an Orange SIM card. It might have been cheaper of SFR, like 0.38 cents a minute.
The only concern I can think of is, I don't think I have ever been in a wireless retail store that had someone who spoke English. That might make it a little difficult unless you know some French.
Any other question, feel free to ask.