Okay, I'm a girl (sorry to invade guys) and normally don't post, but this one I had to.
If you have to play down your intellectual side for a girl, then maybe you should take a good long look at the girls you are trying to talk to and figure out if that's the kinda of girl you wanna be with. Eventually she will realize that you have a brain, and if that's a side she's never seen before, she might decide you aren't the guy she wants to be with.
I myself an a college graduate, as is my boyfriend, and i love to go out and have fun as much as anyone else, but if I can't even have a real discussion with a guy then he's out. I need someone I can have a conversation with, without feeling like I'm talking to a person with an IQ equivalent to a 3rd grader. And it does help to have a sense of humor as well.
If all your'e looking for is a piece of a**, then by all means act as stupid as you want.
But, if your'e as smart as you think you are, then we both know what kind of woman you want to be in a relationship with, and if you would quit hiding your intelligence, you might just find her. Believe me, we exist. I blow off idiots on a daily basis, but I've never once refused to talk to or dismissed a guy who actually had something to talk to me about, in fact that's how i met my boyfriend. Good luck.
(A quick tip) Don't be ****y or arrogant about your intelligence, chances are if a girl is attracted to you (Brain and all) she won't be attracted to an inflated ego and you'll just come across as a jerk to her.