As far as my experience goes, it's not a good idea. A while back, I had just come from the range with my shotgun, when I had to "open carry" it to my friends apartment to clean it. I had to park a few blocks down, and since I didn't have a case for it (I had just gotten it and I trashed the cardboard it came in), I decided to walk with it. The action was open, the safety was on, and my hand was over the reciever (but still showing the open action) with the muzzle angled at the ground. Luckily for me, a Richmond LEO had to walk right past me and notice it. It took forever to get everything sorted out. Even after he saw that it was empty, they still threatened me with a "felony charge". If I had known then what I know now, it would have played out much differently.
In my opinion (IANAL), you should *THEORETICALLY* be ok having it slung on your back with the muzzle pointed in a safe direction. However, it can be almost guaranteed that you'll be eating cement with a pair of cuffs on you and a cops boot up your ass in no time at all.
Going on a hike or walkabout into the middle of nowhere (implying that it's legal to carry the rifle in question)? Sure, why not take the bushy.
Going to a populated place? Leave it at home or in the trunk.