Exactly. I went recently and ended up in San Antonio because that's where the first bus from the airport went. I'd never go to an 'Ibiza club' but in the daytime it was fairly quiet and I had a wander around the back streets, had a lovely lunch in a small traditional restaurant which was quite cheap and then went to the beach for a couple of hours. I then moved on to Ibiza Town for a walk around the marina and old part, which was beautiful.
We've also been to Santa Eulalia for a beach and tapas eating holiday, which was lovely and quiet.
I don't know what 'people watching' is or why it's something to do on holiday but there was two women fighting in the airport while I was waiting on the way back. That was memorable.