Dawn-
While PlanC,
posting them over from home, would in theory be simplest & cheapest, you'd probably need to look into the details. The two primary package services in the US are Fedex and UPS. (DHL has just returned to the market as a new player.) Parcels sent by the post offices as mail tend to be exempt from brokerage
fees, but parcels sent by any other courier service can have brokerage fees imposed, surprise.
Our post office (USPS) will hold mail "care of general delivery" which is our version of "poste restante" but only at a primary post office, not at branch stations. So if you have anything sent that way, you need to confirm exactly which post "office" they are going to. That's free, and I think held at least 30 days. They also rent post boxes, and anything that doesn't fit is simply held for will-call at the counter. They won't rent them unless you first come in with
government ID, so a post box is out if you haven't already been there. But general
delivery is available without advance arrangements.
FedEx and UPS both have franchised retail store locations, and a "UPS Store" usually rents boxes (not mail boxes, only the USPS can call them mail boxes) and has extra services with them, like notifying you by
email when something has arrived. I have no idea if you could rent a box in advance of your arrival someplace, you'd have to contact them to find out. But that's another option for having a
delivery address with a physical pickup location.
American Express at least used to offer parcel holding for cardmembers traveling abroad, I have no idea if you could use a service like that, much less how scarce their offices in the US might be. Between our eternal war on drugs and our post-9/11 hysteria, sending drugs and having someone hold them may be a bit problematic outside of the
commercial options, unless someone has a good personal friend.
Some of the airlines used to have parcel services for unattended parcels. Before there was a FedEx, you could literally send a parcel on a particular flight. Perhaps BOAC or someone has something similar, where your parcel could be held at a US
airport for pickup?
In any case, good luck.