Continuity mistake: The number of knives on the knife thrower's chest holder change throughout the scene.
Audio problem: Why didn't we hear the 18-wheeler come rolling down the street when the little boy was going to get El Mariachi to come with him to get his guitar? He crosses the street and then the sound appears and the truck appears.
Continuity mistake: When Bucho shoots at the limousine glass when it first arrives, the shot on the window changes around a couple of times.
Continuity mistake: During the rooftop shootout Hayek has a red and a black shoe on. At one stage you see both shoes in her hands then there's a shot of Banderas and then its back to Hayek and she's taking the red shoe off again.
Other mistake: How does Banderas shoot the bad guys falling back off the building? It's impossible from the angle he's at.
Answer: Tito Larriva as Tavo says (in reference to Steve Buscemi) that "This guy smells like shit." The name of the song being played is "Manifold de Amour" by Latin Playboys.