EdFred
Taxi to Parking
In my banner towing days we would sometimes sell one-off tows (happy birthdays, will you marry me? etc) in remote locations where banner towing was not common. At that point I would have to get the map out and find a nearby airport to do the tow from. We would always call and ask. On rare occasions the response would be yeah no problem just come on in and do what you need to do. Banner towing is a perfectly legal part 91 operation but more often than not it took an act of congress, special dispensation from the pope and the promise of sexual favors to get airport managers to allow me to drive two hunks of PVC pipe into the grass next to the runway for a few hours and lay out a banner for pickup.
Public use means the public has access, period. It does not mean the public has access to come in and do whatever they want. Take a hibachi into an art museum so you can grill some burgers while you look at the paintings and see how it works out for you.
Both examples are apples and broccoli while comparing the the airport in question.
The transient student pilot (even with an instructor) is not making alterations or performing a commercial operation at the airport. And in your grilling at a museum attempt. Please. This museum is preventing only certain people from even entering the museum.