I often drive by a home, in a state with legal weed, and I can smell the stench from the road ... every single time too, and no, they aren't smoking outside at all times of day. I'm not anti weed, and I wouldn't complain about someone smoking on their own privacy, or even when alone/not around others, but you can indeed smell it from afar. And if you smoke, you know.
My guess is that they are growing pot, not just smoking it. These days you can smell the industrial marijuana warehouses from the freeway in Oakland, inside a car with the windows up.