Correct, anybody can call in and receive this discount. I would suggest calling WDW and telling them you want to book with the late summer discount that starts on the 14th of August. No code needed.
OR, you can book on the website, just scroll down to the bottom of the main page and click on special offers. Select the late summer travel discount and from there it will prompt you to check for availability and then to make a reservation.
The only problem there might be, which I don't know the answer to, are the US offers always the same offers for Canadians? I know the UK has different travel discounts.....maybe someone else knows the answer to that.