If your cellphone company offers service in the U.S. islands, you might be able to make a call from St. Thomas or San Juan on your cellphones. Many passengers on my last Caribbean cruise were doing that. There were, however, a few who were grumbling that they had been promised service and it wasn't working. A prepaid phone calling card can be a great help - I use one I obtained through Travel Guard (after purchasing their trip insurance) and have had good luck with it. Not cheap, but their card offered about 45 cents a minute in Puerto Rico - good enough for a quick call to make sure everything at home is ok!