Apply by tape. There are some limitations for graduate students. See the answer below for details. You can try to arrange an on-campus audition for some other time. In order to do this, you will need to contact the professor yourself.
Some departments are more likely to allow a non-audition weekend appointment than others.
Taped auditions are always welcome. Applicants should prepare the most professional audition tape possible. Remember that bad recording can easily mask good playing. For undergraduates, applicants applying by tape have the same opportunities for scholarships as those who apply in person. For Graduate students, applying by tape will limit your opportunities for Associate Instructorships for Fellowships.