Gosh, I have used the bathroom everywhere.
The worst are usually bars in cities and porta-potties. The ones at a standard "day job" office buildings suck too. No ventilation, humid, lots of stalls, generally smell like they've been cleaned with dirty toilet water.
I use the family bathroom whenever I see one. They are cleaner. Big name stores usually have good bathrooms, like Nordstroms, Bloomingdales, Saks. Sometimes they have music and stall doors that go to the floor for privacy. Sometimes they have a family bathroom... Usually if there's a family bathroom, it's big and single, no stall, your own sink. I am my own family.
I used a really bad toilet last time i was flaring at an ice cream shop. it was no name and there were cleaning supplies in there. A mop in dirty water, flies. It was nasty. I also had to go into a mom & pop shop on the side of a city road once. I was surprised they let me in, and then I probably did some damage, but it only lasted a minute until it cleared. I guess they understood. Their bathroom wasn't terrible considering.
Movie theaters tend to be fairly clean and abundant.
Public transport places, bus stations, train, airport, are usually gross. Grocery store bathrooms are some of the worst.