[jerrya]

Sincerely, what I think you should do is to partner with Mailboxes etc. (or similar) (or even with FedEx) and have the postcards printed in the appropriate local zipcode.

Postcards of the Grand Canyon need to come from the Grand Canyon.

Postcards of the Eiffel Tower need to come from Paris.

This actually makes your play even easier since you don't have to buy as many printers.

This is attractive for your parters since you are selling their services for them, and since you are increasing utilization of their equipment.