Don't let me down/Don't fail me!
 

One of the guys at work just got his nephew a job. He is a young kid out of high school and new to the construction industry. I heard him talking to his nephew and he said, "no me falles!" in a serious but sarcastic tone. I understood this to mean "don't let me down", or "don't fail me". He is from Mexico, but I'm curious if that is a fairly understood expression throughout the Spanish speaking spectrum? Gracias a todos.

Yes I think it's pretty standard, also you could use the verbs decepcionar and defraudar.

I won't let you down. No te decepcionaré or No te defraudaré

"No me falles" is a very usual expression here as well.

Awesome! Thanks guys.