Have they stopped trading? Their utter lack of any manufactured goods would lead one to that conclusion.
So they speak various human languages, N/A, various Spanish dialects, and English. They're also capable of telepathically gleaning intentions from a different species, humans.
If they actually traded, they'd be the sharpest darned hagglers in existence. And yet they're satisfied with peanut butter, fruit, and the occasional cigarette lighter. Go figure.