welcome to the site, i hope it as much use to you as it has been to most of us.
There is really no 'best' place to stay. It really depends on what you want out of your ibiza experience.
If you mainly want drinknig all day and all night, then maybe san an may be best for you!! these are mainly hotels which are all inclusive, but you haven't got to take part in the activites. The age range tends to be slightly younger then ibiza town, or playa den bossa, but they are cheaper. San an has got the controversial west end, the sunset strip, lots of other bars, and two nigtclubs eden, and es paradis
Ibiza town is more gay orientated, it is the more expensive out of the three choices, if you stay in the heart of ibiza town the days are very lazy and the nigts are wild, esp along the port!! the two major clubs are Pacha and el divino. Ibiza town has not got a beach, you will have to go to figuretes for this, but its not very far.
Playa den bossa really is 'clubber orientated' this is because its soo close to ibiza town, and the fact that it has space and bora bora literally across the road from each other, this also has the longest beache in ibiza!! Many will tell you that bora bora and space are the places to go.
Which ever you choose to go to, none of these three places are far away from each other, just a taxi, or a bus ride away.