To speak for someone

[jellybabe]

"No hablan espanol, estoy aqui para hablar por ellos, y el incidente les paso a ellos"????
"They don't speak Spanish I'm here to speak for them and the incident happened to them."

[chileno]

Correct if you are going to talk in their behalf. Incorrect if you are going to interpret for them. In which case you use "para" with "interpretar"

:D