I don't really care too much about nationality, so I may not really notice all the time. But I don't consistently see any Brazilians at any particular clubs. There was one girl who worked at Gold Club and Booby Trap in Pompano for a while, who had the classic Brazilian look, but I haven't seen her recently. There isn't a club I'd suggest going to on the basis of their Brazilian talent, but they aren't so rare you can't just stumble into them at many of the popular clubs. I'm sure if you hit Tootsies on a busy night, they'll be a few, but IMO it's not worth the hassle to go there just for that chance.
There is also very much a tendency to lie like gammanu says. There's a Colombian girl at Cheetah Pompano who is pretty popular, she doesn't look or sound so different than the Cuban girls that she stands out. And she doesn't make a big deal of her heritage, but if you talk to her for any period of time you'll figure it out. A number of Cuban girls have noticed her popularity, and will claim to be Colombian if they think they can capitalize on her popularity.