The Rio currently has a very good room sale going on. The rates do fluctuate, but right now they are better than the negotiated rates for a number of upcoming conferences. You get a room for an average nightly rate of $60 for one upcoming conference.
The Rio does not charge resort fees either, so the rate you see (plus 12% tax) is what you actually pay.
The offer code for the Rio is IRFNF. You can click on the following link to get to the page with the code already active.
https://www.totalrewards.com/hotel-reservations/main/?view=ratecal&propCode=RLV&packageCode=IRFNF
(Dec. 10, 2012 update: The offer code is still good and is showing savings of over 50% off the regular rate for some dates)
(Nov. 7, 2013 update: The offer code is still good and is showing rates of $29 for many dates in November, December and January)