Yah, my ST seem to tend towards alternate year bearing. Last year, one of my trees set so much fruit that two large branches snapped off, wiping out a good 100 or so mangoes. The other problem with such huge crops is that the mangoes are mostly small. This year it has a sparse bloom.
My other ST, though, seems to set smallish crops every year (it's in the very rich / high organic profile, while the other is in deep west palm beach county sand).
Overall, I'm really happy with this year's flowering (and so far with the fruit set as well). Would say I'm in the 75%+ bloom category as well.