We went 18-30's for my 30th. Stayed in the Central City in THE smallest room I've stayed in. A self catering apartment where you could sit on the bed & use the cooker. 2 Single beds pushed together in the corner filled the room, you could only walk single file between the bed & the wardrobe/wall. You had to walk in sideways into the bathroom coz the door hit the basin. That said, it was one of, if not the best 2 week holiday I've had in Ibiza. More to do with the club nights we went to than the 18-30's element. We did pretty much avoid all of the organised rubbish.