i need to know if a permanent resident needs a passport to travel to mexico?

A permanent resident of where? This question needs clarification.

depends on how long you are going to stay, one day over and back you don't need one. but if your going for like a week, ya you do. ( you do want to be able to get back in the USA. Although its not very hard even if you don't have one, LOL Ask Any Native Texan