The Owens Valley is spectacular if you get through it with low winds (it can get a little bumpy in the afternoon, with winds). Cross the mountains somewhere north of Reno, or over Tahoe if you like (this route will take you over Crater Lake as well), then fly down Hwy 395, past Mammoth, to Bishop, and down to the Mojave. Through Cajon pass into the LA Basin, and down to San Diego.
If you like mountains and a little desert, its pretty scenic!