You are probably thinking of the Interamerican University. Yes they also have a flight school on the field, I never really checked if they would rent aircraft to nonstudents, so it might be worth a shot.

Expect to be spoken to in Spanish when the person picks up the phone, this is a local university. Just speak in English, they will understand, it is a flight school!

http://www.inter.edu/en/campus/campus.asp?id=13