I disagree with Jak2002003 above--I've seen hens range awfully far away, no matter how lovely their place is. Mine will go all the way to the back field, even though their pasture is far nicer (our back pasture is fallow right now, and nothing but blackberry brambles). I've seen my Dad's hens on the top of his hill, even though they also spend time in the grainery, which is much friendlier to hens than the hill. I would assume that your hens will decide to fly out some day.
It it true that they are slightly more vulnerable with their wings clipped. You have to balance that against what it adds to their lives to be able to range. We clip all wings so our hens stay in the chicken pasture. When they are let out, they go EVERYWHERE, destroying vegetable gardens and flower beds in their wakes. If I didn't clip wings, I couldn't keep chickens.
Also, I'm assuming that you mean you want to let them out into the garden now, while it's not planted. Chickens in a planted garden are a nightmare. And if they get near any mulched flower beds, you'll start thinking about chicken soup for dinner, LOL.