If you want to get a REAL karting league check out Andersen Race Park in Palmetto; a little bit more of a drive but TOTALLY worth it. It's an outdoor track, almost a mile long, great course, and much faster karts.
here's a video I took there two weeks ago when my buddy and I did an all-day pass for kart rental. They run leagues on Sundays I believe.
YouTube - Andersen Race Park Karting