I thought this post that I found on Storm2K might be of interest to some of our ex-pat residents and vacationers too:
For U.S. citizens, if you either reside in, or are visiting, a foreign country, you should register online at https://travelregistration.state.gov/ibrs/ui/
There are two good reasons to register: Help for you, and information for your loved ones.
A hurricane (or earthquake, tsunami) could devastate the island you are on, knocking out all forms of communication for some time. The U.S. government will try to evacuate you, if they know who/where you are. Don't expect the local government to help you evacuate in a disaster. While they will, of course, have an interest in you returning home, their first obligation and main focus will be to immediate needs of medical care, food, water, housing, etc.
Privacy Act forbids State Department from giving information to anyone regarding your whereabouts, unless you give your permission in advance. So, while State may know you are alive and well, etc. they will not be able to tell your next of kin.