Most guys in Sitges are tourists, but in the weekend also guys from Barcelona come over and it will be much more busy in the clubs than on weekdays
The club to go in early evening is Mediteraneo, it gets started at 1 or 2 at night, and closes already at 3.30. Then the crowd moves to club Organic or Trailer. Both clubs have popular foam parties, don't miss those!
On Tuesday there is the Gay Beach Party in the summer.