I did the following route from Tetons a few years back and it kicked ass road and sights-wise. Highlights include Million Dollar highway in Colorado, Mokee Dugway, Hwy 12, Natural Bridges, Capitol Reef, Bryce, Zion in Utah, just to name a few.
Though, it's gonna be hot for sure, except for a very brief rest in the higher parts of CO. Suck it up and see the sights or be a pussy and run back the way you came

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http://tinyurl.com/232kj8P.S.
You didn't give enough info with your request, like how many days you have to get back...