I'm thinking of mis-translating for my old coworker who feels it's ok to only speak Spanish
That seems mean. Is there a reason the coworker doesn't speak English?
Lack of opportunities... All he does is work. He doesn't have a social life.
It is wrong to give people false information if they don't know the language. It can be annoying but it might help to show him where to take English classes and help him out.
I'm going to tell him what I want.
I get that it is frustrating but you need to help him out. He will learn as time goes on.