I'd like to note that Pokemon is not a game designed for five-year-olds. The card game is a little basic, especially when you've played Magic: The Gathering, but I'd say it's geared more toward early tweens and teens. The anime is definitely a children's show. That's geared toward those individuals at about the age of ten. And the video games? Well, ones like Diamond/Pearl are actaully complex in nature once you get into EV training and all sorts of the other subtle nuances in the games.
That being said.
I don't worry about what people think of me. So, I really don't care if people know I play Pokemon. I collect the cards, and people will often tell me if they've seen one they think I'd like. I just bought a ton of them off my ex-boyfriend's current roommate. I play the games just about everywhere I go, and I don't turn the volume all the way down, so there's hardly ever any mistaking that midi-file music. My car's cd player currently has a mix of the 2.B.A Master disk, the First Movie Soundtrack, and some other random Pokemon songs I've found here and there. I blare that wherever I drive. I'm also currently designing a tabletop roleplay game based around Pokemon, so I'm almost always involved in something Pokemon related.
The awesome thing about my friends is that they're all just as nerdy as me. Only a couple play the card games, and most are sort of disillusioned with the current anime and video games, but the fact is that all of my friends have something super-crazy-nerdy about themselves, and we all accept that about each other.