I've stayed at MANY Motel 6's across the US since the 1980s and this was the grimiest. As a general rule, I've found that Motel 6's in the inner city (anywhere in US) are often run down compared to those outside of town. Be sure to drive around the whole building looking for boarded up windows, etc, before staying there, if you're a bit iffy. That goes for all budget motels!
The only reason I don't give it a 1 star is that the room had a fridge, which most Motel 6's don't offer. But that's likely because there had been guests living there for extended periods. Accordingly, the bedding and upholstery were stained and there was a lingering smoky smell. Surrounding units were creepy, like one that seemed to be full of barking dogs, as if it were a kennel. From the noises, the guests kept strange hours, with transients coming and going at all hours. Security latch on the door was missing. Not very reassuring. And it's nowhere near ASU as was advertised.