To enter this code you need two controllers with no memory card in either slot. Turn on the game. Before the title screen appears hold L1, L2, R1, R2 on controller Two. After the screen flashes, while still holding these buttons press up, up, down, up, left, right, right, left, up, up, down, up, left, right, right, left. If you entered this code correctly you will hear a golf swing. You then will have access to all players.
Highlight a course at the course selection screen then hold L1+L2 and press X.
When chosing a golfer press L1+R1+X while choosing a golfer. This will change the golfer to the opposite hand.