Re: February vs. May
I think you would be better off with a late May trip. The last week of February can be busy because a lot of schools will have that week as a break. You are also getting into the Spring Break crowd times. The weather, as others have mentioned, can be questionable then. February tends to be very rainy in Florida.
Late May is a time that I have been often, and the crowds are usually pretty low. Depending on the year, it can be very humid, so plan on some time at the pool. There's also the Flower and Garden Festival going on at Epcot, which I think is one of the best times of year to see that park. Future World is usually very sterile, but really looks nice during Flower and Garden.
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