Well first off,, depending upon where one is, one can only legally do so much.
Oh imho what one chooses to do or not in public is a matter of taste of course.
For me it has allways been a "is this appropriate behavior for this situation/area" question.
Like, seeing two goth'd out teenagers with one wearing a leash in a public place in some cities isnt all that out of place, might get a few looks, heck I met my Owner and his first wife in a gothrave bar and she was leashed and they both looked all goth'd up and fettishy, but in that venue it isnt out of place, they were both however fully clothed too, go to a small rual town and the same attire and behavior may actually upset some people depending on where one lives.
Having been tught and influenced by those who came before me, some places just don't seem all that appropriate and there is a strong "not involving the uninitiated" veil that still hangs over me to some degree, like if you were to run into my Owner or I on the street, you would most likely have no clue whatsoever that we were into bdsm at all, unless you happened to catch us doing something subtle and be able to observe us at it for awhile, though even then you wouldnt make any solid connection unless you came up and asked...like on occassion, he will have me hold my hands behind my back as if they are cuffed while we were shopping or out and about, maby even keeping me under such disipline while in a resteruant, including feeding me in a romantic way (We just did something like this a few nights ago in a sushii resteraunt, where he fed me by hand, at one point I was even blindfolded).
Have one of strip down and get an anal plug pushed up one's butt in public like on some of the porno's one sees now days or in one of the stories in front of people and you may well be arrested, but that sort of thing imho, is porn, its not BDSM nor is it the way I was tuaght to comport myself or represent the community and the art of submission and would be wholly inapropriate, especially in areas where children may be present.
So it is a matter of "degree as well as location, and activity".