I'd wear one if you're meeting at the alumni's office, especially on a weekday. If it's a weekend coffee shop kind of thing, something more casual might suffice. The way I look at it, you can always take off your suit jacket if the environment is not very formal...
Could all you off-campus interviewees please tell the class when you submitted your Part 1 and 2? I'm trying to figure out if anyone who submitted Part 1 right on the deadline has been invited to interview as yet. Thanks