The best "busking" sites (in the Ft. Worth/Dallas area) for me and/or my trio are flea markets/swap meets.

All ya do is rent a space (usually about $15), and as long as you keep the volume low enough not to interfere with your neighbor's business, all is well.

Last time my trio did a flea market, we cleared, after expenses, a bit over $90 per, over the course of 3 hours.

Basically, it can be a paid rehearsal w/ instant feed-back!