Hi! Unless you feel that you have to spend time in the West End (and before anyone starts, each to his or her own, this is just my personal opinion remember) I would definitely stay in Figueretas. You are only a 10 minute walk to Ibiza Town or PDB. On top of that you can add a good selection of places to eat on different budgets. My favourite place to eat is an italian called Il Vichio Molino in Figueretas where you can eat great home made pasta for next to nothing.
You can always get a taxi or bus over to San An for the sunset strip and any clubs you might want to try.
Have a good one. Only three weeks until we head over.