I have not heard of a predominately gay club, resort or beach on AC. "Openly gay"... this is Central America and AC is a small island. I do think you will find everyone is very friendly while you're there and treats you as respectfully as you treat them.
While I dont know about gays on AC, LilLez, I think all the posters on this board are gay. Not that there's anything wrong with that. (sorry, sometimes you just have to go for the cheap laugh)