Nothing on their Web site.
Robert was able to find a USPS drop box; apparently it’s playing a game of hide-and-seek:
Outside the main entrance between the ticketing and baggage claim behind the Palm Springs International airport sign curbside. Regular blue mailbox.
Robert provided a couple of photos but they were rather small. I was able to find the sign on Google Maps. It may be easier to find if you walk to the main entrance and then turn around.
There is a Palm Springs Air Museum but it’s on the other side of the runway on Highway 111, if you have some time before your flight.
Robert updated recently that the collection time is 1pm every day except Sunday and holidays.
Last updated 22 November 2021