This happens every couple of months here, exactly the same pitch, college students yadda yadda, trip yadda yadda, I usually ask if they have a vendor permit (required to sell door to door) and they leave. I generally call police and report them and they are "asked" to leave town.
The strangest was a few months back, two guys show up at the door saying they are from the phone co. and are trying to upgrade services, THEN ask for my phone number? I said " you are the phone company, you already have it"
They leave immediately and do not go to another house.
Did I mention that when I am at home, or in the yard I OC my 1911