If it's a street and theirs a house on it i knock the door.
As far as i'm aware it's not illegal to knock even with this sort of signage up and about
however, i not knock in daylight and i make it clear i am local, a professional business and it's ME who will carry out the work
do far never had any really bad reations - just a couple of grumps say NO and slam the door but out of several hundred thats not bad.
And some of my best customers have come from these 'NO DOOR SELLER' areas.
this sort of thing is really aimed for the 'want your driveway done' brigade here today gone with a few grand tomorrow.
Darran