Rotorhead, check out "Kokokahi Sailing Club"
Thats pretty much the only active cat sailing club in Hawaii. We have a google group site where we surf.
I'm geussing you'll be stationed at Schofield?
Depends on what you want from sailing a cat before anyone could recommend what to look for, like if you want to just cruise around the bay and have fun or do some racing or both. Most likely a Hobie 16 would be the best for learning on but it might be small for your size if you wanted to sail with others. There is a couple of other boats for sale right now!
When do you arrive?