I visited Costa Rica a few years back and we stayed at a gay hotel between Quepos and Manuel Antonio. There is a gay beach in the area as well. I will try to get the name for you this evening.
One thing you can't miss is Tabacon. It is a resort and hotel. While not a gay hotel, my partner and I did not receive even a side ways glance when we visited.
The resort has thermal springs that create all sorts of pools to relax in. It is unbelievable. Very Garden of Eden-esque. If you can't afford to stay at the hotel, you can still visit the resort for $40 a day. However, I strongly recommend staying at the hotel.
Have a great time.