Yeah sorry, I should clarify in my original post that instead of "interview", I meant "informal meeting". That to me is always acceptable, because you're somebody who needs more answers.
In my position, it would be nice to get an in-person feel for the campus, rather than just getting a sense from what you read online.
However, let's say if I'm on the fence about if I really need/want to visit the campus, then should I go anyway because I will have the benefit of meeting POIs, which could help improve my chances of acceptance? My gut feeling says, "it won't hurt you", as long as everything goes well, professionally.