We were there during spring break. It was crowded. Even at the gates on the day we managed to wake up early for our MM (we had 2, only made 1) it was crowded... we were there at 6:30 and the lines were already LONG just to enter the park! Despite the crowds, we had a great time. However, we have little ones... so we did not ride a lot of the "big" rides. We just did things that were less crowded. We only had 3 big waits... Nemo (45 min), Peter Pan (30) and PFF (40 min or so). Everything else was less than a 10 min wait.
I have been to DW in the summer... and I do not remember it feeling as crowded as it did last week in DL.
My suggestions...
Get there early... lines were already getting long by 9:00.
Leave by 11... swim, eat and take a late nap, return around 5
Unless you are going to see Fantasmic or the Fireworks... avoid those areas directly after the fireworks/Fantasmic. Do NOT try and navigate mainstreet/castle /New Orleans Square directly after these shows... it is insanity

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If you want to enjoy the rides in the above mentioned areas during the fireworks/fantasmic... that works great. They are virtually empty during this time. However, do the rides... and get the heck out of there before the shows are over. If you do get stuck down by SM and the HM... hang out and grab a snack until things clear up. The jungle cruise is also deserted during this time.
If you have a MM and want to ride Nemo... get there early and run to the subs via Fantasy land.
If you want a day to sleep in... go to DCA at opening (10:00). The crowds are minimal and did not get large until early afternoon.
It you go with a good attitude... You will be just fine
