C.M.
Las Madres is great -- I meet a lot of moms at the weekly park days from the Sunnyvale 1990 and Sunnyvale 1992 group and we still get together. (the kids are graduating from high school!)
Also some of the parent participation pre-schools like Cupertino Co-op (actually on the grounds of Fremont HS in Sunnyvale) are a great way to meet other parents.
There were (and I think still are) a bunch of classes for preschoolers and parents (like Gymkids) in the buildings behind the Fremont Union High School district offices on Fremont Ave. (near Fremont HS). I think they are "sponsored" by the Fremont Union High School district as part of their "parent education."
Also go by the Sunnyvale Community Center on Remington and pick up one of their activities brochures. They have everything from gymnastics to art/pottery. They also list all the Sunnyvale pools, hours and swimming lessons.
Have fun!