Yes a "Real" Black Baldie is a Hereford x Angus and that is a very good commercial cow and black baldie calves do very well in most sale barns. Hereford x Brangus is called a "Super Baldie" by the Brangus people and is also a good cross. It is essentially a baldie with 3/16s of Brahman blood giving them a little bit more heat tolerance and insect resistance. They would be (maybe) a little bit better suited for your Florida environment.
The what breed to use on baldies is a loaded question and really you need to determine what it is you want to do with the calves. There is an advantage in a simple two breed cross breeding system in that it is simple. You can come back with Hereford or Angus on those baldies and get 3/4 heifers and come back on the heifers with the other, and so forth and so on. You have some heterosis and following two breeds is easy. For maximum production (once your cows all had their first calves) you could breed those baldies to a Charolais bull and get big growthy calves who SHOULD weigh more across the scale. Simmental or black Gelbvieh is also good in a 3 way cross. You have to be pretty disciplined and know what you want to do 2,3,4,5++ generations out with crossbreeding or you can "mongrelize" your herd where there are 5 or 6 different cross cows out in the same pasture and little consistency in the calves.