So, one person believes that the insect damaging the mango leaves is a mirid. I'm starting to wonder if we had an outbreak of avocado mirids which caused both the swiss cheese avocado leaves (and low fruit set) and the ratty looking new mango growth.
Fortunately, the mango damage is mostly cosmetic at this point, because I'll be pruning all of the affected trees back this summer. So, rather than hit it with insecticide, I'm just going to pick off new shoots and prune out the affected foliage. I think the mirid population will dwindle once the hell heat of south florida summer kicks in.