All of my friends know I think, and family. It's nothing I hide, though neither actively discuss with them, as we simply wouldn't be able to talk much about it, not sharing a mutual interest in it.
Conclusively, no. I don't hide it, though someone would have to ask me about my hobbi-(-es, not hobbit ;D)... Wait.. When someone asks me about my hobbies, even though it was long ago that last happened, I don't think I told many about manga and anime..
New conclusion: I FEEL as if I wouldn't hide it if someone asked about my hobbies, but probably more out of caution rather than fear of being judged; I wouldn't say I read manga, but that I like to read, as a hobby.
This only if the person is someone I don't know, being cautious, as I said, remember?