I think it depends - I wouldn't bet the farm on it. We were there last March and it was in the high 70's for a few days then it was a high of about 63 for the rest of the trip. My kids did swim every day in the heated to 80 degree pool where we stayed, however, I shivered with towels over my shoulders much of that time. IT was VERY chilly in the shade anytime the sun went behind a cloud. I would not have had any fun at a water park. I don't think the kids would have either - staying IN the water they were fine, but getting out to go to a different slide/pool would have been too cold to handle for very long.
Just my opinion.
Oh and we're from upstate NY, so even though 63 was VERY NICE for touring the parks - it just wasn't warm enough to be dripping wet with the cool air on you.