I'd say if you are inundated with homeless people your whole society, walkable or not, is a huge failure and I'd expect unrest any moment - with fatal consequen

I'd say if you are inundated with homeless people your whole society, walkable or not, is a huge failure and I'd expect unrest any moment - with fatal consequences. So I'd focus on that, instead of looking aside and building barbed wire fences to protect your ideal cities.