I believe that most of the stands throughout the parks accept debit cards as well. I rarely carry cash. I think the one exception would be the carts that come out prior to the parades, etc. with the light up toys, and the balloons!
I know at SW the CS at Shamu Stadium did not take CC/DC, and I was rather shocked! (I know that OT, but I was trying to recall if this has ever happened at Disney - just how my brain was working this morning!)