When the guitarist almost gets hit by a bus, you see a shot from inside the bus about what happens outside. If you watch carefully you can see Robert Rodriguez in the rear view mirror holding the camera with a towel on his head.
Director Robert Rodriquez spent a month in a clinic as a "test dummy" to earn the money to film the movie. They only had enough film for one shot. Any of the mistakes found are due to the limited budget available, as they couldn't afford to correct themselves.