I've seldom (if ever) seen this one written up, and it's been one of my favorites since I moved here in 1977. I believe they opened c. 1945, and, remarkably enough, one of the founders still works there!
Anyway, the food: best beef fajitas in town. Best carne seca chimis in town -- imo, of course. Excellent salsa & chips. Good lunch specials, nice people, decent prices. I can't recall a poor meal in 25 years of eating here. That's impressive.
Club 21 is on N. Oracle (E side), between Ft. Lowell and Miracle Mile (if it's still called that). Big sign. Tourist-free.