Federico's is certainly good for a cheap Mexican place. I place it well above any of the 'bertos places I've tried. You get quite a bit of food for your money especially on Tuesdays, where some of the tacos and burritos are $1 or $2.
The Green Chili Burrito is my favorite item on the menu by far with the Carne Asada Fries following a close second. I wouldn't recommend getting the Green Chili burrito to go if you have more than a 4 or 5 minute drive home as the sauce will ultimately soak through and you'll be left with a fairly soggy (yet very tasty!) mess in your wrapper. Eat this quick for best results or be prepared to use a fork if you hit any red lights on the way home.
As Jon K. said below, the drive through is a nightmare. This is by far the most consistently slow drive through I've ever seen. If there are any other cars in the drive through, you should head inside and place your order.
This isn't meant to be an extremely fancy place. It's like a cleaner Filiberto's that smells a lot nicer and has much better food.