It's a gem to find taco trucks nowadays. Don't need anything fancy. If you've noticed the same truck sitting at the same spot for a while, it should be good enough to give it a try (especially if there's a line). But I think it's more rare to find tacos that cost $1 now... So far, I only ran into 2. The first one (2nd one will be posted on a different day) is located off San Gabriel and Hill street in Rosemead. Here, you will find Tacos Los Potrillos located in the LA Auto Shine car wash corner. The taco truck is parked from 5:00PM - 12:AM everyday.
It was extremely hot when we came so we just decided to eat there instead of taking it home. We ordered Al Pastor and Asada. I wouldn't say these were the best I've ever had, but I would definitely come back if I were to crave some. And for $1, you can't really complain. And if you WERE to complain, it better be for good reasons like food poisoning for 5 days. If you got the sh*ts, it's normal... catch the drift? I swear sometimes when people complain, it's like going complaining about going to McDonalds and saying their burgers does not taste like a burger. And to those people that only order 2-3 and calls it quits, how are you even alive?!
So to conclude, for a buck, these were decent and worth the price. Don't take my word for it though, go check it out. It may be obvious, but it's CASH only.