Firstly dont miss the Formentera island, great beaches! beautiful location just few minutes boat ride away, probably one of the best beaches in the med.
KM5 is a place I liked very much, lesser crowd that Blue Marlin. This is not a beach club but a lounge and restaurant with inland location.
Cala d'hort beach has a great fish restaurant called Es Boldado, accessed by car or a bit rough walk from the beach.
Tropicana is nice beach club and restaurant, much more laid back than Marlin.
Right next to Blue Marlin is a place, which I just cant remember the name, which is very nice as well but Blue Marlin really is the nicest, if you end up there on a very busy evening there is plenty of outdoor space to stay away from the loud inside.