Public health recommendations are changing daily: wear a face covering / mask at all times when out; swimming & surfing now banned at every beach in the county. You can only walk the beach if it is within walking distance of where you live. But you can still ride your bike! Karl checked this for us with the San Diego County Health Dept. However, the 6 ft distance does not apply to cyclists. The distance needs to be considerably more. At any speed, you are immediately in the air of the rider ahead of you. Our recommendation for now: Solo Only.
I would like to add to Norval's recommendation which is totally consistent with what are now broader recommendations
https://www.ride-healthy.com/biking-during-the-covid-19-lockdown