From The Jack Benny Program:
Here's proof that Americans could celebrate Cinco de Mayo, although this next clip first aired on Christmas Day, 1960. Jack Benny & Mel Blanc dust off their "Si/Sy/Sue" routine, as Sy (Blanc) brings in the Tijuana Troubadours for Jack's "Amateur Show" to perform the Cuban standard, "Quizas, Quizas, Quizas", the melody of which would be co-opted by ABBA several years later for their hit, "Fernando".
There were no Mexicans involved, as the two guitarists were members of Jack's in house vocal group, the Sportsmen. Not so sure about Sue.
Blanc & Benny would bring the band back, this time as the Tijuana Strings (sans Sue) for one of Benny's NBC specials in the late 60's. The Strings perform "The (Spanish) Flea", soon accompanied by Jack on violin. Although Jack voiced his concern about the Strings being a little too close to Herb Alpert's Tijuana Brass (whom they were parodying), "Spanish Flea" would later be used by Chuck Barris for The Dating Game.
Y'know, I'm not sure if Jack ever had Alpert on any of his specials, which would explain using Blanc and a pre-fab band.