For a different experience in cheap fast food, try any of the hamburger stands in the LA Area. Typically greek owned and have the usual fare:
Thin grilled hamburgers on oversized buns with lots of shredded letuce and thousand island dressing.
Tough pastami sandwiches, but they are large and a good value.
Good grilled chicken sandwiches.
In the Latino part of L.A., stop in at King Taco and grab a few Carne Asada tacos and some horchata.
If you are on a tight budget, stop in a Tacos Mexico for a handful of tacos and a drink for well under $5
I'll also add to the vote for ____'rtos chain. Great for some rolled tacos (taquitos) diooed in some guacamole.