Yes, Polaris would be easily visible (it's circumpolar in the Northern Hemisphere, and being only about 2 degrees away from the Celestial North Pole, it never sets). It's not an extremely bright star, only 2nd magnitude, but since I can spot it without any trouble in my suburban backyard, I think it's safe to assume that Faramir would have no trouble spotting it in Minas Tirith, which would be much less light polluted (torches being far less efficient than electric streetlights!).