Home Postcodes by state SA 5121 Postcode 5121 5121 is the postcode for 3 localities in SA: Macdonald Park, Penfield and Penfield Gardens. Localities with postcode 5121Macdonald ParkSAPenfieldSAPenfield GardensSA Postcode 5121 State or territory South Australia (SA) Localities 3 Council area Playford Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 5120 · Postcode 5125