I went to Ibiza in May. I really never had any intention of going, but my boyfriend said he wanted to go and I was already in BCN to see him, so what ever. We went for four days, and it was wonderfully dead. We didn't club very much, but when we did we either got in free due to our hotel owning the clubs, or we'd met people who could get us in either free or massively discounted. It's not really hard to meet locals. Friends and I tend to stumble upon where the locals are in most places, and drinking buddies are generally pretty quick to form. Having said that, I'm not much of a club person, and I found them a bit overrated. If they had been full, I'm sure I would have hated them. I'm not into massive crowds of sweaty people pushing against me. I'd rather sit in a bar and chill. And even though we got in free, the drinks prices are still unbelievable. And not in a good way.
Ibiza is nice to explore. But I wouldn't bother going there unless I took him along.