I decided to take some data to try and answer this question. What percentage of people out in the streets are wearing a mask? And how does this vary by gender or age group? The short answer, around 3/4 of people wear a mask, and women more than men. To be taken with a grain of salt since this is only for a small sample size, in one city, at one time.
I took the data by observing people near Harvard Square, in Cambridge, MA for a total of 92 minutes on a Wednesday at 10am. I assumed the rough age group and gender of each person from a total of 311 people that came within my line of sight.
I consider “wearing a mask” if the person has any type of face covering that covers their nose and mouth, and included anyone that was walking or biking.
This data set shows prevalent use of face coverings in Cambridge. For every age group, more people are wearing a mask than not (except for teenagers, but that sample size is too small to draw conclusions). The data also seems to indicate that women are more likely to wear a mask than men, especially for people older than ~35.