I take books with me wherever I go; I've learned not to pay too much attention to the "oh-you're-reading-a-'children's-book'-huh" kind of people. I don't only read YA, but that's the genre I'm most attracted to -I think I'm entitled to be, seeing that I'm 17-, and it really annoys me to find people that think they can tell every book you've read just by looking at what you're reading now. And many of those same people don't even read as much as we do. That's interesting.
I heart Ray Bradbury and Isabel Allende, just as much as I heart Stephenie Meyer.
So, like Shesten says, don't judge someone by their cover! Who knows, you might end up loving the book that someone's holding.
ps: I was little, and I don't know how, but I remember MmmBop! And I liked it!
You can laugh at me now... :oP