I think you can do it. When I booked our Dec 2010 trip in the summer of 2010 I used my debit card to pay my deposit because, at the time, I didn't have the Disney Visa yet. I signed up for one after receiving the $200 GC offer in the mail, which was after I paid my deposit. I used my Disney Visa and received the 0% when paying my balance in Oct 2010. I just paid off the balance before my six months was up. Unless they changed something since last summer, you should be fine. I'd double-check, though, first.