Cherie, we have hens, and believe me, they will eat almost anything! We let our girls into gardens when the gardens are finished--they are great at removing weeds and dead veggies, as well as digging up the dirt. In a growing garden they will eat young plants, tomatoes, squash, and anything they can get their beaks around. We have two big vegetable gardens and one small fenced seasonal garden, and let a few of our hens (we have 16, and let five or six out into the gardens) forage. If we let all of them out, they roam. If there are a few out, they stay pretty close to home and we don't have to worry about them hitching a ride on passing vehicles.
You also need to consider predators. Are there neighborhood dogs and cats, do hawks fly over, and do you have coyotes or skunks? If so, only let your ladies out when you are out with them, and can keep an eye on them.
The major benefit of the hens is their manure. Put it on your compost pile for at least three months, or six in cold weather, then spread it on the garden. This stuff is great!