Have ridden Wupatki on our tandem; used all our gears. Nice workout.
As for El Tour de Tucson, this will be my 26th time. My wife has done it 15 times with me on our tandem.
The first El Tour had just under 200 riders, it's been increasing almost every year. Once the riders spread out a bit, it's not bad . . . but +/- 9,000 cyclists is still a good size crowd. The mass start can be a bit dicey.
Pedal on!