I don't know what you're into - maybe you really like anime, and you go to all those conventions: Otokan and Comicon and the whole shibang. Wear your "Otaku" t-shirt to those if you must, but please realize the true meaning of the statement you're making about yourself. Remember that the word is Japanese. Would you wear a t-shirt that says, in English, "I am someone who escapes from reality through my particular flavor of obsession"? Probably not.
Or maybe you would. Freak.