I'd expect most of the parks are packed the last two weeks of March but I was wondering if some people avoid TL/BB since its not yet summer hot during March. Wondering if waterparks are a good alternative during this croweded time.
It really depends on the weather. If it's a warm and sunny March, the waterparks will be packed, and close at capacity early in the day. If it's cooler, they'll still be crowded, but you won't have to be there the second they open in order to get in, and it won't be as crowded during the day.
The opposite is true for DQ. If it's cooler or raining, DisneyQuest will be wall-to-wall. If it's warm and balmy, it'll still be crowded, but not packed.