Did my first ever Spring Break visit to DLR this year. It was the first week of Spring Breaks and it was nuts! We went for my friend's bday, not because it was Spring Break, but her bday just so happened to fall within the first week of it.
It probably was just as busy, if not a tad busier than during the highest Summer season days. I won't go into all the details unless you want to hear them. But just be prepared for lots of teenagers with no parents around.