A new Group Riding Series! will be starting soon, running five Sundays in October and November. More info click here.
Also, be sure to check the Ride Calendar for more opportunities to ride with a variety of paces, including the Bay Area Scenic Trail Rides and Adventure Rides (typically on Saturdays).
https://www.meetup.com/Bikeways-for-Fremont/
Also, check the Comments section at the bottom of the page for occasional updates from organizers or participants.