Welcome A.!
I had the same worries some 30 years ago when we moved to South San Jose. Not to worry...there are still lots of kids in the area (I'm a retired school teacher from the area), and lots of Moms facing the same thing as you. Co-op preschool--check out the ones held at the Santa Teresa Swim and Racquet Club and Santa Teresa Hills Presbyterian Church. Although not a co-op, Clement on Branham was a good one. The libraries all have storytelling hours, and great kid sections. Barnes and Noble also has story time but I'm not sure how often. Find a church--great way to meet other families. I think all the local attactions have already been mentioned, but my kids loved Happy Hollow Park and Zoo. The Japanese Tea Garden is next to it, and the kids loved going to see the fish and blooming trees in the Spring. The Children's Discovery Museum is fantastic and has special attractions from time to time. Lots of good parks in the area too. Santa Teresa Park for a family walk/hike, Cahalan and Los Paseo Parks have good play equipment. Also, for a family outing, try Oak Meadow/Vasona Park in Los Gatos. Lots of nature areas and a train. Youth Science Institute--like a wildlife/history museums are in Vasona and Alum Rock Parks. There are also places of interest in the Santa Cruz Mountains--Felton Roaring Camp train ride, parks, and little towns. You are only an hour and 15 minutes away from the Monterey Peninsula--Aquarium, beautiful walking trails along the seashore, tidepools, and quaint little towns. My favorite is Pacific Grove. And then there's San Francisco--about 90 minutes away. Don't be afraid to explore--that's one of the beauties of a move!
Have fun, and again...welcome! N.