Pick a post office either along your way or at your destination at USPS.Com. Call them and verify that the accept General Delivery Mail (surprisingly, some don't). Call or email your forwarding service and have them send it along.
We use St Brendan's Isle in Florida. They always use Priority Mail and we always allow at least 3 days for or to get somewhere. Have only had this system fail once.
Old (usually dirty) Nissan Titan
Old (enhanced with "male pattern baldness") Sovereign
Young, lovely bride
Goofy dog, dismissive cat