Alright, the best carne asada tacos I've had in town have been at El Gran Burrito, if you hit them at the right time, and, best of all, the northeast stall of the southwest parking lot of Alameda Swap Meet on weekends.
Friday night, cruising East LA for tacos, found a place that's up there - maybe on par with the Swap Meet ones, though different. On third, about a block west of the 710, north side of the street. Friendly, cheery truck, well-lit and well-windowed. Called Y-something. I was there about 9 PM on a Friday.
Fine, fine, fine al pastor, too. Far better than the nearby King Taco, at which I'd just stopped to give my friend Sarah a baseline on al pastor tacos of East LA.