Hi Debi! Thanks for dropping by planDisney.
Try the
Emporium on Main Street, U.S.A. in Disneyland Park if you're on the hunt for a postcard while visiting Disneyland Resort. If they have any currently in stock, you'll probably find them near the checkout area. Ask a Cast Member if you don't immediately spot one, and they'll either be able to direct you to it or let you know if they're not available at this time.
You'll need to bring your own postage, however, as Disneyland Resort doesn't sell postage. Put that on your packing list now! I'm sure you're busy gathering all the things you might need on your trip. We always prioritize sunscreen, sunglasses, and a refillable water bottle. If you check the weather, you might add a couple of additional necessities to that list.
If you've packed your postage and you are able to purchase a postcard, you will have several choices of mailboxes. Spotting them throughout Disneyland Park and Disney California Adventure Park can be a fun scavenger hunt. These pulldown mailboxes are themed to the areas you'll find them in, so they're unique in design! The green ones are so iconic that I even have a backpack with a tiny lock in that style.
I hope this helps!
Elizabeth