I try not to label barking as a breed characteristic as it really depends on each dog. Some breeds though, are more prone to alert than some, and by alert I mean of which a dog hears a noise and starts barking.
If the schnauzers hear someone at the door, or people going by on bikes/walking/etc. when outside, yes they will bark, until the person is out of site. But they are also very protective of me, the other dogs, and the house. If someone comes inside Kiba will continue barking a bit (something we're working on) but she shuts up once I tell her it is okay, but Stryder doesn't bark at them.
I also have a toy poodle, that alert right along with the schnauzers, but not when people come inside, she's a bit wary, but doesn't bark. And the mini poodle, never barks. When he barks I know there's something up that needs to be checked on.