Spring Break at Universal is the first two weeks of April. Look at the park hours here and you'll see they are open until 10pm the first two weeks, then 7pm after that.
http://www.universalorlando.com/cal...o_park_hours.html&year=2007&month=4&year=2007
Now, many people have this idea to do one park a day, but this is a big myth. What you do is visit one park early in the morning, go back to your hotel to rest in the afternoon, then visit another park at night.
The parks open at 9am, so you want to be there 1 hour before they open. The Sea World lot opens at 08:30am, IOA is 8am. What happens when you arrive early, is you get two hours of walk on rides. The crowd usually shows up at 11am, stays until 4pm, then gets tired and leaves.
A few people complain about the time it takes to leave the park and then come back, which I can understand. That's why I usually visit a completely different park. The only negative with that is the parking fees can add up depending on how you do it.
You actually have enough time to throw in a visit to Disney if you want, just depends if you have the money for tickets and parking. It doesn't matter which day you visit IOA, USF or SWF if you show up 1 hour before they open. The crowd arrives at 11am and you leave around 1pm. Rest in your hotel until about 4pm, then come back.
Thurs - USF (morning), rest at hotel, IOA at night (will be crowded).
Fri - SWF (morning), rest at hotel, (Could visit a Disney park at night, or stay at SWF and see the final Shamu show)
Sat - IOA (morning), rest at hotel, USF at night (see KC & Sunshine Band Concert for free)
Sun - SWF (morning), rest at hotel, Do a dinner show like Dixie Stampede
Mon - WnW (morning, arrive at 8am), rest, visit IOA or USF from 4pm - 7pm
Tue - Do favorites.
What you have to remember, is that Thursday thru Saturday, Universal will be open until 10pm and the crowds will be larger during the day. The next week, they will only be open until 7pm and crowds will be less. It doesn't matter what order you put the stuff in. What matters is you arrive a park 1 hour before they open, stay a few hours, leave, rest at your hotel, then visit another park around 4pm.