How busy will Disney World and Universal Studios be on April 4 to April 11?

Since that covers the Easter weekend, it will be pretty busy. Many school systems are on break the before or after Easter, so spring break crowds will be at their peak during that time. Crowds are still fairly high in April in general, but they will likely drop significantly after the Easter holiday week has passed.

Its going to be crowded from now on regardless of the day. I was at Unviversal all day today and it was SLAMMED. The wait times all day for Spiderman 130 min, Harry Potter 120 min. I tried to get a butter beer but I counted 80 people in line just for the butter beer. The three broomsticks and all the stores all had massive lines to get in. The craziest thing I saw was the Massive line for the locker for the harry potter ride. it stretched for hundreds of people. I was hearing it was a two hour wait just to check your bag. Ridiculous. I would not expect much of a change on the date you are planning on going.

April is a busy busy busy time for the Park. Don't forget it is Spring Break for colleges all over the USA. Different schools have different dates off. The week before and after Easter are also big holidays for school kids.AND It's the HIGH SEASON in Florida. Weather is great and not grossly hot and humid like it is in the summer. The park will be packed no matter what days you go during April. Best free advise I can give is do the "BIG" rides that get crowded (Space Mountain) as early in the day as you can. That way you won't have to waste 3-4 hours waiting in line for each ride. Enjoy.

That is around a holiday and the weather is warming up. So it will be very busy around the time your going. But to look on the bright side, you can get fast passes. But they have made some changes on them, so I'd take a look at that. And its april, the weather wont be scorching like it would be in july.