My flock ranges freely, but return to their coops at night. The young chickens only roam around the back yard, but the adults go all over the acre owned by my landlady; I have her permission for this. As the birds mature and get more confident, they will venture out into the front yard and further.
They do this unsupervised, even when I am at work. There is a lot of cover, with trees in my back yard and between my yard and the landlady's back yard.