I suggest to you log onto www.ipanema.com and check out the LGBT section. They can also hook you up with a decent hotel. The big club is The Week which is in a fairly sketchy area of Rio, however, any cab driver will know where it is. Shoukd be about $R25 one way.

The gay beach is at Farme. Look for the rainbow flags. You can get by with just English, Rio is very multi cultural. I do suggest you take a look at threads on FT about safety in Rio. Use common sense and good judgemental and you will be ok.