I carry mine unzipped all the time, with the lock in the slot but not turned. This way if I need anything, I just lift up the flap. I feel like even with this way, it is still secure since the bag itself is a little troublesome to get in and out. I carried it around downtown and it's fine. There might have been maybe only a couple of instances where I had to close up everything because I was in a super crowded place.
Having said all of that, I hope you enjoy your new bag. I love mine, I hope you do yours too.