I know this doesn't answer your question, but have you thought of hiring a car? it can be quite difficult to get to many of the beaches ( even with a car.. ha ha!)
Even when I went to ibiza by myself, it was much more economically to get a car for 10 days than it would have been to get buses, taxis etc every day... and you can go to 3 beaches a day, go when you want, leave when you wnat, pick up randoms and have interesting conversations etc..
Many of the beautiful, more secluded beaches are not even reachable bus.