Sorry, but quail won't stick around without four walls and a roof. If they would, you might be able to cage them only at night to protect from most predators (although hawks and raccoons and domestic dogs and cats and snakes would still get them some of the time). But they just won't. We had one escape soon after we got our first batch of quail. We looked high and low, searched for two days before finally finding her remains at the bottom of our property.
Sorry.
I wish we could do without cages too, but I just don't see it as a possibility with quail.
Now, if you want to raise them and give them a good quality of life, it's still possible. You'll have to construct large flight cages out of fine mesh heavy duty wire, and ensure that it is flush to the ground, and add a wire skirt or concrete footings to prevent things from digging under. If you keep the bird density low and the cage well planted, it's almost like free ranging. Optionally, you could construct cages around the outside and drive the quail into the cages at night, and release only some of them into the flight cage each day--so they take turns using the flight cage in order to reduce the damage they do to plants and soil, while still maintaining a reasonably high density population.
Good luck. I love having quail and I'm very particular about the quality of life for our animals, but free ranging is just not possible with the quail. Ours live on wire, which I don't love, but it keeps the cages clean and I make sure they have weeds every day to pick through and I'm working on adding sandboxes to each cage for their enjoyment. Birds that are being grown out for meat go into a good-sized flight cage where they enjoy life for a few weeks till it's harvest time. It's not ideal, but it works fine for us and I think they have a reasonable quality of life.