I make it a point of avoiding the entire area for at least 2 weeks on either side of the rally. EVERYTHING (rooms, food, etc.) costs more during the rally and the traffic ruins the experience.
Even room availability (at increased prices) is questionable the nearer you get. The last time I found a place 60 miles out of town but that was fine, since I was going for NP stamps. I was able to hit Wind Caves, petrified forest, painted desert, (Mt Rushmore being my exception since I always try to at least see it), Crazy Horse (not a NP... yet), and on to Devil's Tower. Did most of it a little over 2 weeks prior so vendors were starting to set up but traffic was only irritating (and by avoiding the main interstates - painted desert, then sort of w sw to wind caves, then up).