Pay special attention to your composition! Instead of just snapping all the typical, touristy, "look I'm on a beach in the Caribbean" pictures, look for the slightly different shots:
--Frame your shots
--Take your photo from a slightly different perspective
--Look for interesting details instead of just big wide beach or "market" photos all the time
--Make sure you are paying attention to aperture, shutter speeds and ISO so that YOU are controlling your results, not the camera.
And finally:
Practice ALL of this before you leave, every day if possible, so that you are more familiar with what settings to use when.
Even if it's dark by the time you get home, you can at least practice using different settings. Turn on some bright lights, or find somewhere in town that is particularly bright. Then take an object and shoot it in the light, and shoot the same object in a darker setting...you'll at least get some idea of how to change settings given different light conditions. No, it won't be anything like shooting in that bright, bright Caribbean sun, but at least it'll give you a little practice.
Oh...and one last thing:
TAKE ME WITH YOU!!!!

I was supposed to be going on a cruise about the same time, but had to cancel it due to a family situation. Blecch!! I love the Caribbean!