There are many places that have fog, but no or little rain - the skeleton coast inwards/Namib desert in Namibia for example.

No, that's not true; it's just less efficient because you have to handle more air and cool it to a lower temperature. Air in Earth's atmosphere always has significant humidity. See https://news.ycombinator.com/item?id=30716765 for some calculations.

It's reasonable to condense drinking/cooking water from air with solar energy in places that lack secure water. Not water for other purposes; you can't run a cooling tower, irrigate a field or an orchard, water a herd of cattle, or even grow a garden that way. But a household-sized dehumidifier powered by a household-sized solar panel can certainly make enough water to drink and cook rice.

On the other hand, if you live in semi-arid desert or any wetter biome, a cistern probably has a better cost-benefit ratio. Depending on your aquifer, a well may be better still.