It may be off the strip but I think this has to be one my favorite hotels I've stayed in Vegas.
Prices are moderate, freeway is not far off as well as the strip, good rooms and friendly staff. I was also kindly given an upgrade and damn, it was the nicest room I have stayed at Rio. Beautiful restroom, nice room with a nice view of the mountain!
Valet is also free, just make sure to tip well!