Externship: Multiple Interviews same company

I recently completed my 2nd semester in a BSN program and have applied for externships in my area. The location I preferred was not listed on the hospital's main website so I applied for different locations. Immediately following this I found an opening at my hospital location of choice on a jobs website and applied. I have an interview set up with the other location, about an hour away, which is a field I have found interesting and definitely special, Oncology, while the location that I want to work at in the long term, literally a stone's throw from my residence, is saying that they can not continue the process there until I complete the process at the other location.This is an ER position. As a student I am unsure of which area I really want to work in, but both of these areas interest me in different ways. Should I mention in my interview that I would much prefer the other location?? Nothing is certain and I did not want to lose both as nothing is certain at this point. Advice??