Castle, will any of those carriers activate a CDMA iPhone4 I bring from the states?
Not sure about the Iphone 4, but I brought down a 4s from Sprint and it was a huge pain. They were trying to charge me 4k to supposedly get it unlocked and it wasn't going to be 100 sure whether it will work properly. I ended up selling it as is for cheap. I still made money as it only cost me 49 USD, but I wouldn't do it again. Now if the phone is from Verizon then I think it's easier as from what I understand Verizon does not mess with the sim card.
Also you guys should be aware that Claro is slowly getting rid of their CDMA towers. I had a blackberry (CDMA) that is activated with Claro. It used to work, but now it gets no service in Cotui and surrounding areas. Only in Santo Domingo was I able to get service with it. So GSM is the way to go and I would only get phones from AT&T or T-Mobile in The US.