Mine are almost 9 weeks old and they free range. The only predators they have when the free range, unless they make it into my fenced yard, is cats. But we recently "lost" a couple of chick eating cats after they got one chick..
Edit: BTW, after the one attack, they have developed their warning system already too (right now they are not free ranging by the adults, some will start this weekend)
They spent about 1 week in their coop/run (2 nights I had to put them in their coop, just cause they were scared of the ramp). Then I let them free range supervised for a couple of days, and now I leave for work at 6 am, and they are out and about until about 9 pm. (As teenagers, they do stay out later than my adult flock). When I am home, I do check on them a couple times a day, but they are so funny you can't help it.