Unlimited money
When the game asks for a nickname, put in the word BOVINE. Choose the checkmark to exit. Now choose the rest of your options and then start your park. At the Park Screen where you see the park entrance, press and hold the Square, X, and O buttons. The noises you will then hear are your money increasing.
Max Prices
Enter "BUD" as a nickname. Then at the park selection screen, press Square. After the game begins, maximum prices may be charged for the concessions, games, and park entrance.
Extra Cash
During a game press and hold Circle + Square + X. This cheat may be used as often as you like.