Thanks for the recommend, xandros9.
Looks easy peasy. Take any American phone. Just get it unlocked if it is not.
What do you have now?
Or are you listing the ones you have because you want to upgrade the camera you take?
Carrier choice is limited. Your data will most likely be limited to GPRSor EDGE most places when traveling between cities and 3G or H+ in resort areas and major accommodations. I wouldn't even worry about the emerging LTE there.
On the 2G any carrier there is on 900/1800 which is standard for radios here and everywhere really.
On the 3G they want 2100 (which really means 1900 uplink/2100 downlink. Also standard for any radio in the Americas.
Oh... Found a cool new reference page, BTW.
http://www.worldtimezone.com/gsm.html