Ok then... If you want to party, you have chosen the best cities to do it. Madrid is well known for its "Marcha", you can go to Gabbana, Capital, Palacio de Gabiria.. etc. I think the best for you will be a hostel in the center, then you can walk to restaurants, night clubs and some museums. Try Metropol Hostel. This hostel is very well located, very near from "La Puerta del Sol".. it's economic, clean, safe, no curfew, breakfast included, and internet service.

In Barcelona, to go out in the night, avoid going to Maremagnum.. Ask to a taxi driver to take you to Santalo Street, it is full of bars and near from several discoteques: Costa Brava, Otto Sutz, Danzatoria... are some of them. A good hostel here....try Gothic Point,, it's from the same chain as Metropol... Also located in the center, near from Picasso Museum.
And Ibiza... I don't remember all the names of main nighclubs, but try to get passes in the bars (near the port)... The best one is "Pacha", "Space".. and sorry but I don't remember the others...For accomodation, we went to a hotel... but don't remember the name.