The scene of the Tetons, I feel like I know like the back of my hand. I definitely need to get out to monument valley though at some point. It just looks amazing. May I ask how big a park it is, and how long it takes to explore?
I'm not George, but since it is in my backyard, so to speak, I thought I'd provide a brief reply to your query about Monument Valley.
A trip to Monument Valley could take anywhere from a few hours to a few days. Monument Valley is a Navajo Nation Tribal Park and, while there is a 17 mile (unpaved) loop road through the park that provides numerous pull-outs & locations for photography, the remainder of the park is off-limits to tourists except when accompanied by an approved Native American Guide.
This makes sense to me since it is home to many people who live there and work the land. In addition, many locations are sacred and trespassing for any reason would be inappropriate.
The park road is open daily from sunrise to sunset. Times vary with the season, but I do not think the hours would allow you to take advantage of the best light. Cost to drive the loop road was $5.00 last time I was there.
If you want to get off the loop road (highly recommended) there are a large number of guides and tours available ranging from 1 1/2 hrs to half & all day tours, as well as sunrise and sunset tours. There are also several guides who specialize in Photography Tours. My recommendation is to go with one of the specialized photography guides who are familiar with your needs, know when and where to find the best light, etc.
I have promised myself that on my next trip to Monument Valley I am going to do the Hunt's Mesa overnight photography tour. http://www.navajonationparks.org/index.htm