We went end of March this year, and the weather was great. Warm but not too hot - sunny and 80-85ish. It got just a bit nippy at night, but not too bad. There were a few days where it would have been fine to do waterparks.
I would think the water would be a little cold though. I don't think they'd have enough consistently warm weather to make the water warm. But we did not go to the waterparks, so that's just my opinion, not based on experience!