The photo at the top shows a stand on Soto Street, just north of Whittier Blvd. I stopped there because it was the largest of the set-ups I passed, and I thought it might have the best food.
Guys walking along the sidewalk respectfully greeted the woman running the stand with a cheery "Doña," which told me that this must be a neighborhood institution. Others stood around with trays of tacos, eating on the spot. The boy at the back took the money ($1 per taco) and supervised the condiments.
Although I was a stranger to the neighborhood, I was quietly welcomed and allowed to take photos. It was a lucky choice for a random stop.
To find this and other stands, drive along Soto between Boyle Avenue and Whittier Blvd. Clothing for sale was lined up on a fence on the other side of the street, so you might end up with something to wear along with your tacos.