You could probably take Amtrak to Harrisburg and take this bus from the train station to Hershey.
http://www.cattransit.com/routepdfs/sep10/Route_322_Hershey.pdf
Keep in mind this bus runs M-F only and runs about 10 times a day in each direction, so it's not like you can just show up anytime and catch the bus.
The "Hershey Intermodal Center" stop should be about a 10-15 minute walk from the Days Inn which seems really popular for interviewees.
Also, someone in last year's thread said the Days Inn in Hershey will run shuttles to both the train station in Harrisburg and the medical school on request. That'd be (by far!) your best bet if that information is true.
Also, if you're not pinching every penny, you could just get a taxi from the Harrisburg Amtrak station to your destination in Hershey.
These are the possibilities I can think of (I'm from the area)... the bus looks very doable if you have to, but I would recommend finding a hotel willing to shuttle you around, it's the ideal situation. This is not a public transport friendly area.
ALSO - for anyone flying in... you can fly to BWI and rent a car. AFAIK public transport from BWI-Hershey is poor or nonexistent (both BWI and Harrisburg have Amtrak, but to get from one to the other, you'd have to go through Philly). The airport very close to Hershey, Harrisburg International Airport, is MDT. Days Inn's shuttle should pick you up at MDT if you arrange beforehand, or you can get a cab. If money is the biggest issue over convenience, I'd price out the cost of flying into BWI and renting a car vs. flying into MDT and getting around via hotel shuttle. Flying into MDT isn't usually all
that expensive, it's my home airport and I rarely find it's worth it to drive to BWI or any other airport.