I don't know how open you are to a new phone company, but I recommend T-mobile over AT&T and Verizon. I won't even go into the horrors I experienced with Verizon on my landline.
Anyhow, I've got an android-running t-mobile device and I've been to Europe, Mexico and North Africa with it and it has never failed internationally. No unlocking or locking to deal with--it just works. Also, with android I can ssh into my computer if I feel like it--not that I do other than to experiment with an arduino controlled cat door, but, hey, I think that's cool and it bodes well for the eventual development of third party apps for things like cars.
Just a recommendation for android and t-mobile for whom I have never worked.
Nissan LEAF™ SL trim, brilliant silver