All I can say is that I see my enemies before my companions do, and I have a fairly high Perception. I can also attack them before my companions "see" them. So, your Perception is what you set it at, not what your companions have. Now, they may see enemies quicker, or rather react quicker, than you if you set them to Aggressive.
However I would avoid setting any SPECIAL to a low Value, unless you want to gimp part of your character for Role PLaying or a Challenge or you just have to have one or two Stats set real high. Me, the lowest I go is 3 or 4, the highest is 7 or 8 on any of them. I try to have some balance in each Stat. That being said, a character that is Gimped in one way or another can be a fun build to play, just be prepared for the limitations.