Salon Los Angeles has seen Frida Kahlo dance with Leon Trotsky, Che Guevara and Fidel Castro with dance hall regulars and revolutionaries, and a lot more. And so, “Miguel Nieto, whose grandfather opened Salon Los Angeles 80 years ago this week, refuses to quit, even as his gray-haired regulars dwindle, even as developers dream about turning the nightclub into condominiums like the concrete apartment tower going up across the street.”