It was "Caraca's", though, not "Caracas". So the idea is it's a restaurant belonging to someone called Caraca, which does sound Mexican in a generic kind of way. Okay, it's a bit arbitrary, but I think the apostrophe saved it from being a total clanger.
And Jim's been good at mental arithmetic in previous episodes, and was a victim of nerves here. Wouldn't condemn him for that one.
The Columbus and "el" incidents were worse.