H.S.
Hi A.!
You should go on to meetup.com and do a search for the East Bay Playgroup. The organizer lives right there in Hayward. I have been part of the group for a year and a half now, and my now 3-year old son has made some great friends there, as well as I've made some great friends. The calendar is always full of things to do, so you should definitely check it out!!!!
Hope to see you at a playgroup or mom's night out soon!