How is it for clubbing? I don't know where the major venues are with respect to PdB, San Ant, or Ibz Town.
Ibiza Spotlight has a great overview on their website.
The biggest ones:
The clubs with the "big names" are in Playa d'en Bossa: Hi & Ushuaia (personal opinion: both are overrated).
In Ibiza Town there are Pacha & Heart - and some smaller locations.
In the middle of PdB & San Antonio (San Rafael) you'll find Privilege, Amnesia and Underground (about 15 minutes from both sides)
San Antonio has Ocean Beach, Eden & Es Paradise.
I personally fell in love with "Eden" (San Antonio) and their sound system (as mentioned above), too. My favorite club on the Island. Nevertheless you can reach all locations by (disco) bus (at least in a normal season).