I agree with what Greg said about kites and boards. Things should warm up some in March but I would still bring a full wetsuit based on current indications. As for camp grounds, I've not stayed in any out of the Keys and can't make recommendations. They are listed in the first stickie at:
http://fksa.org/forumdisplay.php?f=89
The second post also has some useful information.
Have a good trip!