Hi, Doug-
If you can find your way to Colfax, California, I can take you on a nice hike in the Sierras.
I've always wanted to go to the Grand Canyon and Death Valley, but haven't found the opportunity - and I don't know that I'd want to do either in August. I don't know what's the best time of year for Grand Canyon - winter is best for Death Valley, late Spring for Yosemite.

-Joe-