Ha. My cousin has like two dozen chickens, and they follow her to the coop each night like soldiers. She did lose a few along the way, and maybe it was for the best. I'm definitely not going to be chasing chickens down the street. If they want to strike out on their own, then I wish them all the best. I'd rather 2 obedient chickens than 4 rebellious ones. If it takes some selection pressure, I'm ok with that.
I'm on my phone and I'm super lazy - so we should probably talk on the phone about this... Chickens are dumb and awesome. The eggs are fantastic. When you get them, lock them in the coop for 2 days straight. This seems to reboot their brains and they go in there on their own every night. I never once had to chase a chicken. The closer it gets to sundown, the closer they got to bed. Seriously. So dumb. And so awesome. While they can and may hop/fly over that fence... I doubt they will. And if they do, they'll come back. Honestly - I'd chuck a cheap/temp fence up from the side of your garage to the back fence and let them roam that whole area. You can build/buy a simple coupe to close them in at night. Keep it simple. Keep it easy to clean. All the stuff everyone else said. Let em roam.
Maybe if you get chicks, they'll imprint. We inherited our chickens from our landlord- they owed us no allegiance.