We stop by Don Tortaco's a lot at night when other things are closed. It's basically a Roberto's: cheap, greasy food. The food is generally pretty good, and they are quick.
The downside to this place is that it's really, really inconsistent in terms of pricing and the way the food is made. If you want rice and beans in your burrito, some people charge you $0.55 each, and some people charge you $2.00 (the combo price). And the amount of extras is always different. Sometimes it's like a tablespoon, other times it's overflowing. It's all just really inconsistent. So if you like to order the same thing and expect to get that same thing every time, this is not a place for you.
Also--the service here is always crappy. I wouldn't expect much from a place like this, but I feel like it needs to be said. The cashiers are usually pretty unfriendly.