I wear socks/stockings in outdoor sandals. Most people do unless they are on holiday, I would say. Stylishly dressed women might wear thin nylon-type stockings in open-top shoes, but bare feet are kind of... not taboo, but really frowned upon if you're not being extremely informal.

Mind you, I am no expert on this. I'm not particularly perceptive when it comes to clothing, or style, or things like that. Which also means that I'm a little shaky on exactly what you can and can't call a "sandal" in English