Here are a few more cheats for you to try.
Up, Left, X, Triangle, R1, O, O, O, L2
Gangs Members Everywhere
Similar to the 'Gangs Rule the Streets' cheat, except all pedestrians are replaced by gang members. Policemen, firemen, paramedics and shop owners stay the same.
Left, Right, Right, Right, Left, X, Down, Up, Square, Right
strange cars have hydraulics. Pedestrians become fast food workers and clowns. CJ wears strange outfit.
Triangle, Triangle, L1, Square, Square, O, Square, Down, O
Up, Down, L1, L1, L2, L2, L1, L2, R1, R2
L1, L1, R1, R1, L2, L1, R2, Down, Left, Up
a thanks goes out to edisoncarter at GTAForums for finding them.