Greetings Kyoko!
Sending Disney Postcards is such a fun thing to do and receiving them is equally awesome!
I love that you're planning to send postcards overseas while you visit the
Disneyland Resort.
While there are certain
mail services available as well as plenty of postcards to choose from when you visit the shops at the theme parks and the Downtown Disney District, stamps are not currently sold on-site.
In order to purchase stamps you would have to leave the resort and visit the nearest US Post Office, which I believe is located about half a mile north of Disneyland on Ball Road.
If you happen to be staying at one of the
Disneyland Resort hotels, you may be able to receive complimentary postcard shipping, subject to change and availability.
If you purchase your stamps ahead of time and arrive at the theme parks with your postcards addressed and ready to mail, you can drop them off at one of many mailboxes located throughout the parks.
Just to give you an idea, the
Disneyland Park has nearly a dozen mailboxes where guests can drop off letters and postcards! You can find find one of them on a green lamp post across City Hall on Main Street U.S.A.
I hope this information is helpful.
Have a magical time at Disneyland!
-Anabel M.