Wait, I'm confused... I thought colleges had safe zones that BG won't enter. And if a BG stumbles in to one by accident, then the student can whistle to remind him. If the BG is deaf, then the student can use a call box to call security.
I'm sorry for my sarcasm to an otherwise legit question. Campus carry would give the students that are eligible an opportunity to carry and as others have said, the BG won't really know who is or who isn't armed.
In regards to your other question, I don't want the possibility that any private citizen can put up 1 and only 1 sign to cover both open and conceal carry. I can see a lot of places that would want to put up an open carry "NOT" sign and I don't want the risk for conceal carry "NOT" as well in the same sign.