[chuckh]

Ok, this may not work for you, but here we go.
Go north to get south.
Head up thru Portland and over to Spokane (the Columbia River Gorge is picturesque)
Cross into Idaho and stop for a few days around Coeur d'Alene (beautiful area).
Head south east down to Yellowstone National Park for a few days.
Head south thru Salt Lake City and on down I15. About 15 miles south of Beaver, Ut. turn east on highway 20 to go over to Bryce Canyon National Park.
Backtrack back over to I 15 and head south.
You may want to make another stop at Zion National Park.
Continue south on I 15 on into Las Vegas.

Its a long route, but I guarantee it will not be boring.

What ever you decide to do,,, be safe on the road, and enjoy the trip.