They've always been packed every time I've ever tried to use them. The one's I have tried had horrible unforgiving customer service and the food was mediocre after very long waits.
For mediocre food there are far more efficient choices. (like White Castle two blocks away, or the food court at the easily accessible nearby mall.)
I wish you better luck with them than I had.
I haven't had great food from them yet, it's been hit or miss.
I think, though...you've essentially got twenty restaurants there. If you go when they are packed (which I usually end up having to do as well, not sure when they aren't packed), you're getting what you get at any restaurant--a staff dealing with being slammed. And with trucks, you're also getting people who have to deal with being slammed while packed with coworkers into a dorm fridge. I think the odds of bad service are higher.