How do i activate cheats in mercenaries 2 for the ps3?

i have tried everything that i have found and nothing is working. There is cheats for it and here is the website the i went to and found them at.

http://cheats.gamespy.com/playstation-3-cheats/mercenaries-2-rumor

Does anyone know how to?

Press L2, R2(2), L2, R2, L2(2), R2(3), L2 to enable cheat mode