Left Wing would probably be the term you're looking for, as the American and European (and in other parts of the world) definitions of liberals have some major differences, but yes, the majority of the board leans to the Left. That being said, the admin of the site and many of the mods and posters are conservative leaning, so it is welcome to people of various political beliefs.
As MLB correctly stated, how you are treated very often comes down to the manner in which you state your beliefs and whether you back it up with evidence rather than solely what you believe. We have had as many liberal posters who have run into trouble with other members as we have had conservatives. The bottom line is, if you argue in good faith, back up what you say with evidence, and treat people with respect (which amounts to a lot more than just not name-calling), you'll be treated fairly even if people disagree with what you have to say.
Anyway, welcome to the board. I hope the political leanings of the majority of the posters here are really the least of your concerns, because it's not important for most discussions here.