People briefly walking by each other (in opposite directions), outdoors in the fresh air, probably are in very little danger. From what I've read about the spread of this virus, the danger comes from immediate contact between their germ-laden droplets and your nose or mouth. In other words, as you walk past each other, and one of you sneezes or coughs in the other person's face, that would be dangerous. But otherwise, probably not.
The odds of catching it are probably reduced the less time you spend with other people, how could it be otherwise? But I really think being afraid to go out for a walk is kind of on the level of hysteria.
Right now, I'm trying to decide what to do about food shopping. I'm not running out yet, but this pandemic is supposed to last for many more weeks, or months. Eventually, I will need to restock. I've never used food delivery services, but I'm thinking about it. Not sure how safe the supermarkets are.