There's more good roads to ride a motorcycle near LA than you might think.
California Highway 33 has this 35 mile stretch of twisty road along our route below. See larger map.
California Hwy 2 is another outstanding ride in the LA vicinity, as is Hwy 39 to Falling Springs. Check the LA County website for current road closures.
Mt. San Antonio (aka Mt. Baldy) is the highest peak in the San Gabriel Mountains, 10,000 feet at the summit.