When you use Priceline, use the name your price option and start very low. For example, our DS's trip is in May, I started a couple days ago and place a new bid every night, starting $25 for 3* and 3.5* hotels. Got one 3.5* yesterday for $32/night. Adding up all the fees, the final cost is about $45/night.
When you check in with priceline reservation printout, please first let them know you are the whatever program member. Most of the hotel will not honor your points because of the priceline reservation, but they still have to treat you as a program member.
Even the basic room at Westin should be way better than motel 6. So, I would gladly pay $65 at Westin for a basic room (regular rate at over $200) via priceline any day.
My friends have told me that they slip a $20 with the print out at a Vegas hotel for a multiple days stay. They got upgraded to a premium room.