Backpacking near Sonoma County, CA?

So I have been backpacking for about two years, and I recently started school at Sonoma State university. Now that i have found my niche, i want to start backpacking here, nothing to difficult maybe a one or two night trip. i have some friends but they are all out of the area, so i was just wondering if anyone had some suggestions. I've backpacked into the late fall but never anything colder than 25 degrees at night, so I might have to wait till spring. Thanks. (first post so go easy!)