You will have to check with your cell phone company. Many of them don't have coverage, some have coverage but with extra fees, and some have coverage in some ports but not others. You might try their website for more information. I have T-Mobile and they have coverage in the Ukraine but nowhere in the Caribbean. Go figure.
Cell phone will not work while the ship is at sea because there is no cell station near by. You have to check with your cell provider as to which countries he has service with. You may be lucky in that your provider has services in the western caribbean; just check. Bring the phone along and use it as an alarm. Also you may need it if you encounter problems getting to or from the ship. Good luck.
I'm with Cingular and to my suprise, when I turned on my Cell when we were in both Cozumel and Caymen Islands, I had a signal. Although I just turned my phone on to see if I, in fact, did get a signal, I didn't want to pay the roaming fee for checking my voicemail out of the country. Now my cousin, who is with Verizon, only had reception in Cozumel, and didn't have any reception whatsoever in Caymen Island.
I have T-Mobile and had perfect service in Cozumel but not Costa Maya(well...thats to be expected) but when i dialed it was in spanish and i only speak half of that langauge and from what I heard it was "we're sorry but we can not route your...." so i guess i didnt really have service there.....take it along with you; its not heavy, it might just work. Hope this helps....have fun!
I have Cingular and was able to use it from Jamacia and Grand Cayman! My wife wanted to check on our daughter! The bill was less then I expected. Only $75. We made about 4 calls from Jamacia and 4 from Grand Cayman.