Ooops,itchy trigger finger!
Should have said, lively nightlife, so you may want to base yourselves elsewhere and visit.
If you look at a map (
http://www.ibiza-spotlight.com/beach/island_ma p_i.htm)
Starting at Santa Ines on the West coast, all the way round to Cala llonga are nice places. There are nice untrashy places on the south too (Jondal, caleta), but as i said before, north is quieter.
Ibiza spotlight has some good info on different towns, so worth a browse of the website.