Some Burros is hard to beat for cheap and unhealthy Mexican. Even a place like Filiberto's that competes strictly on price is an afterthought for me. I can go to Some Burros for almost the same price, and while the portions are smaller than Fili, you actually get decent food.
I really like the red burro with beans. The lean beef chunks are stewed until they are fork-tender. I also really like the beef and potato tacos, which is a combo that can be hard to find.
They have a lot of tasty options on the menu to keep you coming back. However, I try not to eat here more than once a month or so, as it's carb and fat overload to eat at a place like this often.