When is the best time to go is dependant upon what your priority is when you get there. For us it is not TOO hot and lower crowds. We can pretty much take vacation any time of the year so this is an added bonus. My sister is a school teacher and she knows that whenever she goes it's going to be busy.
That said:
January -- lower crowds, colder weather maybe
February -- first part is lower crowds but second half is busy, can be cold and rainy, stay away the last half because of President's Day and the Daytona 400.
March -- weather is usually nice but school breaks make it busy
April -- the best month if Easter is not in that month.
May -- lower crowds the first half, but it can be hot (in 2002) it was in the high 90's every day. My DD was 7 months old so we spent a lot of time in stores (that's not a bad thing)
June, July -- can't say because I've never been there in those months
August -- very hot, less crowds at the end
September -- can be very hot and it's hurricane season ( I think everyone should experience an hurricane once in their life. Ours was a category 1 and that was scary enough for me.)
October -- busier but more moderate weather plus there is
MNSSHP to go to. (It's definetely worth the time and money)
November -- first half is great, stay away during the American thanksgiving. This is my favorite time to go. As you can see below that's when we're having our first trip home.
December -- tied with November because the crowds are low, the weather is temperate but can be rainy, but the Christmas decorations are fabulous. Plus you can go to
MVMCP and the Candlelight Processional. Stay away over Christmas though.
I'm sure this doesn't help your decision, but have fun getting everything ready.
