Our first trip to Universal was Wednesday May 22 to Friday May 24 2013 before Memorial Day. Wednesday we did Universal Studios and the park was not crowed at all. We did almost all rides by 2:00 p.m. and walked onto almost every ride. Thursday we went to Island of Adventure. We stayed offsite, but booked a package so we were able to do early entry. It was a little crowed but due to our clutch in our air-conditioner we had to leave early afternoon to get it fixed. Friday was a mad house. There was school groups and the crowds was thick. We went to ride Spiderman, it said 45 minute wait but turned into a 2 hour wait. It was maybe three when we left. We were driving down to Miami for a cruise on Saturday. In IOA we only did the Harry Potter area, Seuss land, and Superhero area. Loved Wednesday but hated Friday. Spiderman was worth the wait!
This is our family experience and someone with more knowledge may have a different view.
Hope this helps!