In August of 2019 the San Diego County Board of Supervisors adopted a cell antenna ordinance that contained a provision for a 300′ setback between any cell antenna and any school, church, police station, etc.
It’s not the easiest thing to find on the County’s website.
https://www.sandiegocounty.gov/content/dam/sdc/pds/advance/SmallCellWirelessFacilities/Final%20Ordinance%20Strk.Underline.pdf
Here is an amendment to the County’s zoning ordinance from September, 2019.
https://www.sandiegocounty.gov/content/dam/sdc/pds/zoning/update101.pdf