I stayed at Bally's over Thanksgiving for < $20 per night - but an additional $40 per night resort fee. The resort fees are what kill you. I'd try the Eastside Cannery. It had a lower price and a lower resort fee.

I've stayed at the RIO a few times for fairly cheap as well. One more place that I stayed at that looks more like a motel, but there is security is the Alexis Park. It's a 3* and the rooms are decent. I think the resort fee was lower too. Near the former Hard Rock (now Virgin)