I was talking to a Haitian friend recently and he said something about his daughter’s wedding… he said mete sou pa dèyè. I understood that he meant he’s fallen on hard times – is that correct?

Yes, mete sou po dèyè (mete sou po bouda, lage sou po bouda) means to impoverish. The wedding expenses might have rendered him penniless.

Haitian Creole ↔ English Reference, Look up Haitian Creole and English Words