Mindfulness is great, but in my case I noticed that the usual techniques don't work. I needed to find my own techniques. For instance most autistics have some kind of special interest. Diving into that certainly helps me. It's where my mind can roam freely.
Calling is OK for me.. Getting called now? That's hell. Totally no control over sensory input (that infernal ringing noise), no control over who or when or what they want?
It helps if you can find a place that has the least negatives, like maybe it has some seats that are usually free and not too close to the music, or a place that has some noise absorbant wall coverings. Maybe if you can do some scouting or ask friends for help selecting a place?
Had a pretty good interview with myself an hour ago when I was asking me how to improve health care by offloading technical procedures to nurses rather than having them done by doctors. I agreed with myself that e.g. taking blood samples is better done by nurses who are really good at it, how it's not just a skill but an art, and how having really proficient nurses would increase their overall job satisfaction, would lead to higher quality health care in general, lead to lower costs and better patient outcomes. I agreed!