Swing Away Golf Cheats
To get every single golfer do this: when you are at the main menu enter L2, R2, L2, R2, Up, Right, Down, Left, L1, R1. You should hear a sound and all characters should be available in Stroke Play Mode.
Left Handed Golfers
For your golfer to play with his left hand, highlight him/her hold L2+Select and press X.