It depends. I am over 50. I live in the Washington DC area. People my age, and even younger, are wearing pantyhose quite often. Definitely at work (I've got several 30 years olds and, when really dress up, they all wear very sheer, nude hose).
Now, if this dress is on the more casual side, summery, flowy and you are wearing sandals, then, no on the pantyhose. I wear hose with pencil skirts and close-toed shoes, very sheer, you'd hardly know they were there but they definitely make for a clean line and flaws disappear.
It's sometimes hard to know what to do because if your legs look really bad then no-hose can be far worse. But some people, no matter what age, have great legs.