Apple Store will receive shipment on a daily basis, so keep checking on apple.com. Once Apple Store does receive stock, then apple.com is updated show that it is available for pick up. If you manage to get one, then they hold it for 14 days.
Agree I can't believe they never had other customer with PO Boxes to not have a way to use different shipping then. If it is the same, you can usually start refreshing Apple Store a little before ten until next day stock shows. And 40 miles isn't too far to get a Green right away. I got the delayed email at the last minute Friday so checked Saturday and found a 256 SIM Free Green 50 miles away and went for it.