Any advice for using your Unlocked AT&T device in France and Europe in general?

[gadgetdaddy]

Have some family traveling to Paris and wanted to know if anyone can chime in on some advice for using GSM service abroad in France and other parts of Europe and should the service be purchased before they depart, or is it best to pick up a local GSM card once in Paris?
Any advice would be helpful.
Thanks

[rich hathaway]

ah paris, wish i had the answer cuz that would mean ive been there :D but i havent, why dont they contact the place they are staying and ask them?