Open all reasonable hours of the day, closes when people stop buying food (usually 3am-ish). This is the quintessentially local Los Angeles experience. Its clientele are mostly its working class Hispanic neighbors. The tacos are simple, cheap, and come with as much salsa as you want to pile on yourself.
At 3am enjoy the comings and goings of the more eclectic locals - the ones who only come out after dark. El Gran Burrito is well-lit and always feels safe. During the day, both indoor and outdoor seating are available, at night only outdoor seating is available. L.A. weather being what it is, always sit outdoors, the better to people-watch.
It's not on the menu, but you can order a vegetarian taco. El Gran Burrito is near the Vermont/Santa Monica subway station on the Red Line.
Su-Sa: 06:00-23:00