We got a 3 day pass when we were in holiday in Salou, used 2 days in the theme park and one in the water park. To be honest I wasn't that impressed with the theme park, and would have preferred to do 2 days in the waterpark, but the ticket didn't allow that.
I felt that we really covered everything in one day and only really went back the second day as we had a ticket. There are a few big rollercoasters and some smaller rides and not very much in-between.
I would say it was fine for a visit, but not sure I would spend more than a day or 2 there.