I've had no problems with law enforcement in the U.K. parading my GG on the streets and sometimes on public transport. Although, I suspect in London where I am, the police are educated about these types of
devices.
I have, however, had a couple of problems in some public venues indoors from people who are ignorant of these
devices. Doormen in bars/clubs, for example, haven't always taken kindly to my GG, probably thinking it's drugs paraphernalia.
There are ways to be more discreet with the vapour production which you'll discover with use. Incidently, vapour production outside isn't as significant as it is indoors.
You may want to respect that many people aren't familiar with PVRs and it can freak them out in areas not designated for smoking. Some esmokers take the precaution of gaining consent. Others think sod it, I'm not doing anything illegal, I'll get on with it.