[Latest post in my Google+ Collection, Language, Logic, Life.]
Feel free to walk, however, and breathe. (No wonder the sign attracts graffiti.)
Also, the word 'refrain' has a slightly quaint or archaic air. I heard it – usually accompanied by 'please', as here, or by a sarcastic 'kindly' – a lot in my childhood. Even then it sounded a bit old-fashioned.