Just got back from Orlando area yesterday. This was my 4th trip to Fla., my 3d to Disney World. All previous trips were in March or April. Every trip after this will also be in March or April, or fall/winter!!! We had fun, but it is incredibly hot!!! Maybe if you're south of Kentucky, it won't bother you too much, but it definitely slowed us down some. The crowds at Disney weren't too bad, except at midday at Magic Kingdom. (Then again, I'm from Chgo...)
If you';re going to theme parks - GET THERE EARLY! I mean, be in the park by 9am. There will still be a huge mass of people entering with you and travelling down Main STreet or the main thoroughfare of the park, but the initial crowd quickly disperses. Then about 10:30-noon, there are huge crowds of people pouring through the entry while we were leaving for pool and lunch break at our resort. Even at Magic Kingdom on a Sunday, we rode every ride in Fantasyland (except Dumbo) before 10am and just walked right on. Before 10:30am, we waited only a few min. to ride Haunted Mansion and Big Thunder Mtn. Railroad. The lines started getting long shortly after. The crowds also seem to thin in late afternoon/evening, esp. at MGM.
We had 4-day passes to WDW, but only made it to 3 of the parks, MK, Epcot, and MGM, and still didn't manage to do everything, though we did all the highlights and the things we most wanted to do. We also went to Gatorland and Kennedy Space Center for 1/2 day, Cocoa Beach pier, and went kayaking at Merritt Island Nat'l Wildlife Refuge. You can also walk around here. It's 45 min. from LBV, and a nice relaxing day away from the busy-ness of Disney.