If you go through Death Valley, I would say Titus Canyon is a "must ride". The basement tour at Scotty's Castle is pretty interesting if you are into residential engineering solutions.
Red Rock Canyon and the Mojave are pretty interesting too.
In 10 days you do do a loop: LA>Mojave>Red Rock>Death Valley>Las Vegas>Lake Havasu>Escondido (Stone Brewing Company)>LA
"Don't go gettin' all snotty on me just because I like to drink beer and piss off the porch once in a while." - Boondoggle