There are a few catamaran guys trying to organize in Charleston, SC for sailing out of Sullivan's Island at Station 12 St. Check out the facebook page for "Fort Moultrie Beachcat Sailors":

You could meet up with them and see the different boats most people sail (mostly Hobies). From what I've heard, there are at least a couple guys out there every weekend. I went over there a couple of weekend ago and the people I spoke with were really nice and liked talking catamaran sailing. So, I'm sure someone would let you ride with them and start showing you the ropes.