I bring my 3DS to college and basically play during breaks or in between classes. A few times I've had people say things like "Wow, you STILL play that?". It happens, I suppose. I don't really mind it. In my experience, most people have been really cool about it. In high school I used to randomly give out Pokemon keychains to my classmates. They loved it. I've always been very open about being a Pokemon fan. I think it's important to show people that we aren't all 12 years old.
When it comes to Pokemon, people often say that they've just "grown out of it". I don't think that's the case. I just think that some of us are able to recognize the long-term appeal of the game and value the core RPG and strategic elements, while others don't see past the marketing for younger audiences.