Usually young black kids they have become outstanding acrobats.  This guy was doing things Mel mentioned Olympians strive to do and he was doing it on an uneven brick street!  (He was even too quick for my flash.)

Notice the guy in the red in the upper left.  He's working the crowd for tips while the others did the stunts.  The one thing we noted was different from other places (namely New Orleans) is the "collectors" were very courteous and weren't pushy at all.