We were there this past week (President's Day week) and it was really, really busy at Wizarding World. You had to get a return time ticket.
We were there for early entry on Thursday and Friday and as we left the area at 9 ish, there were throngs of people entering. Even as we got to the entrance of the park, waves and waves of people were still entering and walking over the bridge to get to the park. I was very surprised at the crowd level.
I think Spring Break will be crazy.