Don't know of any AP owned/run POs that are open on a Saturday (except in December).  Only ones I have ever seen open Saturdays are AP agencys and they are usually located in shopping centres and do not do deliveries of anything.  All deliveries in my area come direct from the area sorting centre at Frenchs Forest and if not delivered (always carded and never actually delivered even when at home) dumped at the relevant PO for collection.