Before you go there and get a SIM card you need to make sure your phone is unlocked to any network which most phones are not. The carrier generally has it locked to their network only and it takes them a couple of days to provide you the unlock information.
I ran into that problem before when I went to Jamaica with my local SIM card I purchased. My phone was locked to AT&T network and could not use the other SIM card. They did not get me the code until after I got back which was useless. Once it is unlocked it is unlocked forever and you never have to do that again.
