Before it closed (so sad) I used to always go to a place called Highland Grounds
(yes, there is a step there but they also had an accessible entrance too) I loved their food, atmosphere, etc. As I kept showing up, the waitresses became more and more comfortable with me. One day the manager walked up and said "Eva, can you show me how I can communicate with you?" So my aide gave a little explanation and we tried it out. She gradually brought every waitress over to see the demonstration. So eventually I could just roll in and order myself. They didn't make a huge deal out of it and the desire to learn was absolutely sincere. It was just like learning my communication was the next obvious step since I came there so much. This might not seem like a big deal to you but to me it meant that they saw me as a person worth speaking to and not just 'that disabled girl'.
The difference between this and what the barista did was enormous. Now, the barista was being nice and this was the first time she'd seen me and I understand that she didn't have time to get to know me, so I will give her that. But talking to me that way at our first meeting is like when someone yells "HI! HOW ARE YOU!" to a deaf person. Its instinct but you've got to get over it.
I hope this story helps.