Kelley Park in San Jose is pretty cool, if you're historically minded. It's essentially a small town made out of old buildings (1800s-early 1900s) that were moved to the site from other locations around town when they were in danger of being torn down. There's a streetcar track down the middle of "town" with free rides on historic streetcars on weekends, and you can tour a big shop where enthusiasts restore old streetcars. Weekends are the time to go, because they have a lot of docents, historical recreations and such going on. And you can go into some of the houses and stores, which are fully furnished to the period. Haven't been in years, but it was pretty cool. Fun and historical, but also like walking through the world's largest-scale model railroad layout :-). Here's a URL
http://www.historysanjose.org/visiti.../history_park/
If I were you, I'd also take a long drive down Highway 1, from Santa Cruz to San Francisco, or vice versa. 1 is a great road that parallels the ocean alongside undeveloped farmland and rolling hills, and there are a lot of little towns and beaches off it that are worth stopping at: Half Moon Bay, Pescadero (stop at Duarte's for cream of pepper soup, and visit the old-time fruit stand/roadside attraction nearby, or just hang out in this ancient farm/fishing town), Davenport (some funky artisan's shops, including a massive glassblowing operation), and others. And between Santa Cruz and the San Mateo County Line, especially, there are plenty of wild, undeveloped beaches that you can't see from the road but can hike or climb down to with little difficulty. Gorgeous, chaotic cliffs and rocks, totally unlike Southern California beaches. Just pull over wherever you see a couple of cars parked by the road (they're probably surfers) and follow whatever path you find. You'll get there. It's all more or less public land, but they lease a lot of it to farmers, so don't walk through the middle of any crop fields you find unless you want to risk a snoot full of pesticide (they spray).