OP, do you have an account? If so, hope they send a coupon code. You can also join their Facebook fan page; I've heard that they sometimes put coupons there.
I would recommend getting the digital download instead of a print. I believe it's the same cost, but you get the rights to print it elsewhere and more than once, which of course is way more valuable than just the ONE print of the picture. Same cost as a print (or approximately the same), but more value.
Like the previous poster I assume you're already back. If so, the following will NOT help you, but will help the other person asking questions.
http://www.disneyphotopass.com/previsitoffer.aspx is the link to PRE-order the CD. The CD gives you the rights to print the pictures anywhere you choose. That link can't be gotten to in any other way but to click on it.
They do not have an expiration date anymore, so you could order when you want to. When you order now, instead of it being like the "old days" when you had to hang on to an email with a code (that expired), it now just plops the discount into your photopass account. So when you are back from your trip, have edited all your photos, and you go to order the CD to be shipped to you, that credit is sitting right there.
Some people have photopass cards sent to them...that has nothing to do with the pre-order of the CD. You can use it, but you don't have to, and you can always get all the cards you want from the photographers.