Well I'm going with a bunch of gay friends for a week and we are doing the following:
Matinee @ Space, Gorgeous @ Space, Bora Bora, Circo Loco @ DC10, La Troya (either @ Space or @ Amnesia). These are all guaranteed a good gay turnout and will be very gay positive (indeed La Troya and Matinee are gayer than gay!).
We haven't decided which Pacha night we will do but the DEF MIX and Defected nights will have a lot of gay boys as will Release Yourself.
Basically stay away from Eden and Es Paradis in San Antonio and you'll be fine.
Ultimately of course Ibiza is about the music and the atmosphere and being with good friends irrespective of sexuality. But that being said, some planning is advisable!