Nobody will really notice or care that you're wearing a diaper if they do happen to see it. But people are usually so wrapped up in their own lives and things that no one really notices.
We all know babies and some toddlers wear diapers but I never notice them wearing a diaper because I don't take notice to what's under there pants.
So the same would go for an adult wearing a diaper I would never know that you're wearing a diaper and if I did I wouldn't say anything.
Many adults and older kids and teens need to wear diapers and they do so without any problem.