Yes, I have found that it is very often best to simply sit down at a piano and play (and act completely ignorant and naive if/when anyone comes racing out of the corners to confront me) than to ever ask first. This is unfortunate, as my inclination would always be to respectfully request permission, but I find I am much more likely to be shooed out the door without a second thought unless they hear that I can actually play the instrument with respect, at the very least, and reverent joy at best.
If they still can't hear that or appreciate it, then I'll be shooed out anyway. I just have to remember that no matter what their reason for doing so, or if they are "justified" or not, ignorant or not, or whatever, that this is their right to do. I do not own these pianos, but only temporarily "borrow" them, if I am lucky. Whatever I might think of the establishment, or how they keep their precious (or so-called "precious") instrument, it is still THEIR establishment and THEIR instrument to use (or not) or abuse (or not). Hard to accept, sometimes, but still true.
Sometimes I get annoyed with myself when I catch myself feeling kind of artistically entitled or something... as if the music, the art supercedes all petty concerns of ownership, power, politics, property. I may think that way, sometimes but the world doesn't work that way, and it hardly does anyone any good to get annoyed over it.
I digress...
