At www.scummbar.com on the Monkey 5 page on the audio exerts it says there are 4 secrets of monkey island and i was hoping someone could tell me what they are

Basically the secret is discovering Monkey Island and surviving, because the legend has it that you don't come back once going there.

Actually the secret of monkey island is that the giant monkey head is in fact a robot that only the monkeys from the island can use.
You find that out when you complete Escape from Monkey Island.