United States Post Office 36 Chestnut Ave, South San Francisco, CA94080 Conveniently located in the Safeway shopping complex at Chestnut Avenue and El Camino Real, this United States Post…More Office is small and quiet, offering basic mailing needs. It doesn't have a stamp machine, so if you need to purchase any you'll have to wait in line. It offers mailing and shipping services like most US Post Offices, and it also has a small room of P.O. Boxes. For more information about this U.S. Post Office, please visit them online.