Good question. Let's put it this way, Berkeley the school is a bastion of liberalism, but the only reason it is perceived as that is because the liberal people are the ones that get publicized by the media the most. I mean, would the news stations broadcast news about some guy living in a tree to try to save it, or would they talk about some corporate people trying to change the tax code to help companies?

There are plenty of "conservative" people (however you define conservative) at Cal, they're just less vocal about it. I think the key thing about Berkeley is that people are respectful of diversity and differences in opinions. They actually value that instead of stifle it. Sure you'll get jabs here and there from your friends (mostly joking), but people won't think of you as the enemy or try to kill you (unlike some more radical liberals and conservatives alike), if that's what you're worried about.
My best suggestion is for you to visit Haas and see for yourself. You'll definitely have most of the people be anti-Bush (if you're worried about the political leanings of the population), but there will still be enough conservatives to make you feel comfortable. As long as you respect others, they will respect you.

And terp06 is partially right, Haas is probably less radical (I wouldn't say more conservative) than the rest of Berkeley, but if you're open to learning from them as they are from you, you'll do just fine.