I discovered an odd thing in the game. Park a car right across the entrance to the Ganton gym, jump on it, and run into the top of the yellow marker. It may take a few tries but eventually you will get into the gym, still standing on the car. Once you're in the gym, turn around and walk back out. You will be in a corridor, with the inside of the Ganton gym door facing towards you. If you run sideways you will fall into some white space for a while and respawn on the street outside the gym. Another alternatitive is to enter the jetpack cheat: L1, L2, R1, R2, Up, Down, Left, Right, L1, L2, R1, R2, Up, Down, Left, Right, and fly around in the white. Be warned when you do this though, you can't get back onto San Andreas if you fly off in the Jetpack. You probably don't believe this will work, but just try it.