Popa,
There is a difference between outlawing something that directly affects us vs something that has the possibility to affect us.
We have to actively do bris mila. We aren’t actively required to look at signs. Since there are so many women dressed inappropriately on the street, men should be walking by looking down at the ground wtih the occasional glance forward to make sure the path is safe. He has no reason to look above doorways at signs.