That late in season? Don't count on being able to backpack. Skip the PCT - the sections that are most worth doing will be under snow. I start backpacking on the coast in late October and come back to the Sierra in May-June as the snow melts. Unless we are wanting to go out in snow.
First time in California I would be a sightseer, not a backpacker. Go to the sequoias or the redwoods (two different trees, same species, different locations) depending on weather. Go see Yosemite valley. Go to Point Reyes. Go to San Francisco.
Not too many people ski????
We backcountry ski, cross country, telemark, downhill, snowshoe, etc. - there are resorts in the national parks and over every high pass. People are up there skiing today, in fact. Snow is still falling. Tahoe is a winter sport paradise. Yosemite's Badger Pass grooms some of the roads for cross country skiers.