They won't work on the ship. You can contact Cable & Wireless which is the most common phone service in the Caribbean and activate your phone. You could also try your ship's e-mail. Most of them have it by now.
Tom, the only phones that work at sea are those very expensive ones that work off a sat. The best way to keep in contact if you MUST, is to either use e-mail or phone from the ports. What we do is give them the # of the ship and tell them if there is a dire emergency then call, otherwise, we are on vacation. <G>
Our cell phone worked in San Juan, but it wouldn't work in St. Kitts. In fact, our phone was "home" and not even roaming in San Juan. We live in S. Texas and I guess San Juan is part of our area. I have sailed out of New orleans before, and once we entered the gulf of mexico, my cell phone started working again. I think it all depends on your home service. I for one, will wait until I get to a port if my phone doesn't work because $14-15 a minute could well be spent otherwise on my vacation!