I have had the smae question. There is not one in the World, but you can search for one on their website and it will show you exactly where they are on the map.
When we went this past May I had a hard time finding really good coffee. I usually drink dunkin donuts and then my second choice is starbucks. I felt the coffee was blah there. but I drank it because i needed my coffee fix
If you are staying in a villa ( and even regular rooms)I know they have coffee pots there maybe you can bring your own starbucks from home and make it in the room.
If you are staying at the Polynesian, bypass the idea of Starbucks and head towards Kona, or Kona Island (a coffee bar) where fresh Kona coffee is brewed on the spot.
The Kona Coffee at Kona Cafe and the little coffee bar in the Poly are awesome! It's our favorite coffee at WDW. Other then that the coffee isn't that great except at the sit down nice restaurants. They brew fresh coffee and its okay.
If you're looking for mochas or lattes my mom found the coffee stand that is between canada and england to be the best at making those type drinks. They use real chocolate in their mochas so thats probably why my mom liked them so much.
*le'sigh* Only thing I am not looking forward to this summer is Disney coffee. Everyone has scared me. I'm deffinately bringing beans and a grinder in my luggage to brew some at my Villa.