Trying to figure out the cell phone thing...

[Anabeth]

Doing last minute planning for my impending reach this week. The only thing I have not taken care of is the cell phone issues. I am not totally savvy on this topic and would love some advise from the experts. Was just going to leave my phone home, but realize it will be needed occasionally. My question is, will I be able to buy a plan that will work on an iPhone which does have a SIM card but is currently with another carrier that does not have international service. Can I assume I could just buy a sim for that to use while in JA. Will it affect the phone when I return?Or is it best to just bring and use my galaxy no longer connected to a service...it then being my toss or giveaway....I know there is something about unlocking because of cdma or GSM, is that going to be a factor? I have read up , and if locked , pretty sure I can do the unlock myself.
I would appreciate any advise or insight...