Trekking North in My Favorite Month

October. October! My most favorite month of the entire year is finally here! Temperatures in Southern California are heating up again (mid 90's are forecast for the next few days.) In my head, I'm dreaming of sweater weather, leaves underfoot and full moons bright enough to howl at. I'm hoping to get a taste of Fall next week when I trek up North. I'm thinking of heading up a day early (Wednesday as opposed to Thursday) and exploring some of my favorite sites up north. Any suggestions for one trekking from Los Angeles to Fremont, San Francisco, Berkeley and the surrounding areas? Not so much shopping (though paper arts and book stuff are always appreciated) but more, things to see and take in. Big trees and greenery are always loved and appreciated. Thanks in advance.