Well last year we were too anxious so we would head out at 9 or 10...and hit the bars and get to the club at midnight which might have been a little early but gave us a chance to find a great corner ..you'll know exactly when you get down there....do what you please is the best thing :d
We usually sit around the pool on the loungers, just chilling for a bit, having a few drinks at the hotel before going out about 11ish - just basically saving energy for when the night really gets going
Apart from Space Sunday, we go out around 10.00pm - into Ibiza town - grab a meal, then drinks and either onto a club around 1.00am or continue drinking until we fall over - which usually happens at Dome cos the waitress likes us and puts a little coke in my Jack Daniels LOL.
Wow 10 days from now and I'll be laid on beach in Mykonos will my girlie constantly comparing it with Ibiza (I know who'll win though )
Clubs tend to get going after 1am, but usually head off to one of the bars about 10/11pm, just after dinner.
If you're going out in Ibiza town, say Pacha or El Divinio, it's nice to be able to stroll around the place before going out to the club. Obviously this is a bit trickier with Priviledge and Amnesia as they are located on a busy main road.