I ride frequently up Lake from Mendocino up and above Altadena traffic is light to almost non-existent, particularly after dark. I am somewhat leery, though, of the lack of shoulder and that concrete drainage canal.
You can always go up Santa Anita to Chantry Flats, just climb the gate if it's closed. It is creepy, though, especially with the Deliverance clan, the occasional wildlife, and the possibility of going over the cliff and never being found again.