We have been using the military discount yearly, sometimes twice a year, since around 2009. We have always managed to get into the resort of our choice. Sometimes we have had to go with a more expensive room category, but we still save $$ compared with Disney's discounts. Not once have we had to settle on a resort other than the one we were hoping for. Good luck!
I have never booked a room until after the discount is announced. I've always just taken my chances and hoped that the resort we want would be available. So far so good.....