Its an English expression. It just means that people would be eager to run away. People would usually say it if you said something bad and the response would be 'they'd run for the hills'

I have a different slant. A: Do you think the people working here would like team-building exercises? B: I think they would run for the hills. . It if purely figurative. Noone would run anywhere. It means that they would probably not think it was a good idea, probably not queue up to join, maybe take action to not get included, selected, whatever.

It is an expression that means they were scared and run. The running for the hills part basically means trying to hide.