Jim, Nothing's cheaper than free, but Skype without wi-fi is a non starter. If your phone is out of contract, AT&T will unlock it then you can put a local SIM card in and use it locally. If you just want the phone for very occasional or emergency use, call 611 and turn on Int'l Roaming for the month you'll be there. Calls are about a buck a minute.
But Skype is by far the cheapskate way to go- especially for calling back to USA.