While birds of prey are a real threat, if your chickens are not the kind with head feathers that obstruct the view (like polish, silkies etc) AND your chickens have good hiding places in their area like low bushes etc, then they have a pretty good chance of eluding predation once they are full grown. A rooster for protection wouldn't hurt either....
Personally, if you have a 6' tall VERY secure privacy fence - ie dog PROOF - and you have some shady and hiding places for your girls....AND you lock them up at night - they are so very vulnerable at night when they can't see what is coming to get them and can't escape in a confining coop in the dark - then I'd be OK with doing what you are suggesting.