the only time of year that no irrigation at all is needed is the rainy season, which coincidentally corresponds with hurricane season (who'd have thought?).
actually, building 3 m high beds really isn't very practical in florida, since the sand will run off during the rainy season. that being said, i'm sure someone has built it and will argue...
what is a much better solution is to dig a hole, throw away the sand somehow, and put a bunch of organic matter in there, and plant into that. or consider sunken garden beds. it's soooooooo worth the time to experiment.
the rainy season veggies are the fall veggies/winter veggies. a surprising number of northern vegetables grow great during our winters, like onions, carrots, cabbage... i could go on...
so yes, try building a sunken bed or an in-ground, woody bed. and see how that works out!