i've done it. a friend and i went for a ruck march from my house in lilburn, down cole dr., right into downtown lilburn, and back. granted, we were stopped when we had gotten almost all the way back (we'd been about 2.5 of the 3 miles total) by lilburn police. i had my AR slung in a tactical position over my chest, and my friend had his AK slung over his shoulder, muzzle down. we were both wearing BDU's, and carrying full rucks (full of ammo cans, which were full of ammo). the cops stopped us, and took our rifles to run the serials. this is where i discovered how stupid some cops are about firearms. when calling it in, one cop called my friend's AK and AK47, when it was in fact a SAR-1. he also didn't know how to take the safety off so that he could rack the bolt and check the chamber. one of them did know how to charge my rifle to ensure that it was clear. the three cops told us that we'd have to get a ride back to my house in one of their cars, that we were scaring people. they searched our packs a little (nothing serious, just opening up the top flap to peer inside). now, admittedly, this was not all that smart, and could've ended up really bad if those cops had been a little jumpy or something. and you know that we would've been portrayed a gun-crazy kids that were off to shoot up the school down the road.
my advise is that you not draw attention to yourself in such a manner, having done it myself. it's nothing really fantastically cool. it is legal in GA, so long as you do not brandish your rifle (don't point it at anyone or act like you're going to shoot it in public). however, like i said, it doesn't take much to excite some cops, and the media loves to spin those sorts of things against gun owners.