Remember some companies prefer to recruit in the fall, some in the spring. Even though you may not graduate till spring, don't assume your favorite company will be at the fall and spring career fairs. Remember most companies will be sending a specialist recruiter and a generalist recruiter. If you don't get the answers from one - try the other. You will note that hospitals hire medical staff AND accountants, business majors, writers, etc. etc. etc.
ALL companies use public relations, graphic and computer grads.
They may have them in-house or contract out. The recruiters WANT you to ask them questions, so don't be shy. DON'T SHOW UP THE LAST HALF HOUR of the Fair. Recruiters are starting to pack up. Ask the recruiter what the next step in the process will be.