Most will consider applicants without post-college experience. But even at schools like Stanford, it's literally 1 - 2% of the class.
Fresh college grads usually have stellar academics (usually near the top of the class), stellar GMAT, and exceptional extracurriculars (i.e. fundraising for a student organization isn't exceptional).
High 600s won't do it as a fresh grad. Try 740+.
Also, unless you were some super overachiever - you were a nationally ranked athlete, you were a performing artist (musician, actor, etc.) at some professional level, or you have some exceptional leadership activities (starting a *real* business with full-time employees, significant responsibilities over some large organization, politics, etc.) you really should try working for a few years.
Alex
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com