I have never been able to get mine to work in Florida, but I think it is because I need to get some kind of code for it to work out of my area, and being technologically challenged, i have never figured out how to do it. Sorry to not be any help; I am looking forward to seeing an actual answer to your question.
You have to set it to roaming if it is out of your area (the directions that came with the phone should show you how). But mine worked wonderfully in November 2001 when we were there. I am planning on using it again next year when we go back.