This might help you in picking a weekend. Sep, Oct., and Nov. have quite a few events happening...jeep jamboree, land rovers, mt. bike racing, trail marathon world championships, music festivals, triathlons... http://www.discovermoab.com/calendar.htm
Looks like there might be a small window with a lull in activities in town, October 15, 16, 17. (Mon - Tues - Wed)
It's immediately before Jeep Jamboree starts.
Hmmmm......