spring break (march/april) is very early in the year for ibiza. The party scene doesnt normally get going until late may early june. If you enjoy trance/dance music and like clubs it will be paradise, everynight each one of the major venues has "its" night. Example Manumission mondays, at club Privilege. The 4 major clubs are Privilege, Pacha, Space and Amnesia, there are several smallers clubs and bars all close together, it whats called the westend.
great beaches great weather save your money and go mid summer