We do not free range at our farm. However, we have a very large space where our poultry roam and it's protected by electric poultry netting. We've not had the best experience with free ranging, lost half of our flock due to predators.
Our birds had steered clear of the road when they free ranged, but it also depends on how "street smart" the chicken or bird is. My mom accidentally ran over and killed a guinea because it ran into the middle of the road.
I used to let my chickens out of the coop as soon as I woke up. They would range until about 7:00 P.M. Then they'd go back into their coop to roost.
I've never had a garden, but our chickens pecked the crap out of our flowers! I'd say they'd probably eat your plants as well. However, some people let their chickens poop on their garden before they plant anything. Chicken poop is a natural fertilizer. After you plant your plants though, you'd need to keep the garden enclosed.
If predators aren't an issue where you live, I'd go for free ranging. We definitely can't do it here in rural Southern Illinois, we live right by the woods and our road is a red gravel road. (People drive like idiots and drunks on our road, too. Aha!

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