First, put in the code for the moon gravity cheat (2them00n) - the 00 are zeros - then go into the game.

Get to Beverly Hills.
Afterwards, go to the building with the bikini pictures on it.
Wall-Run-Up to the first ledge, then double-jump into a wall-run-up onto the top of the building.
THEN TURN OFF MOON GRAVITY.
Run towards the accessory shop, while still on the building.
You should start running through the raised part of the roof.
Once you're in the roof for about a second, then double jump.
You should fly through the air into a grassy area.
Turn to your right, and you should see a hedge and the backside of the fountain walkway.
Slowly make your way over to the hedge. If you are slow enough, you should fall through the floor. Afterwards, look for the side that doesn't have the elevator, but has the bus, and then go there.
You should end up in Santa Monica!