I agree with Linda Hopkins. Special Quesadillas were invented in Imperial Valley. There are at least 6 restuarants in Imperial Valley that serve them. Camacho's, Celia's, La Hacienda El Centro, La Hacienda Imperial, Nana Dora's Brawley and El Zarape in Imperial. I have never seen Special Quesadillas anywhere else but Imperial Valley. Not even in Mexicali, Mexico a city of about a million people just across the border from El Centro.
I think the original La Hacienda (now closed) in Imperial made the best Special Quesadillas.