Not only do humans not bark at strangers outside our house, but most of us don't feel the need to yell, scream, or shout at them either. A good amount of dogs, on the other hand, hear someone outside and are overwhelmed by the urge to talk to them. Really, dogs? Are you that attention starved that you have to reach out to people on the streets? Even if you are, you should know that yelling isn't the best way to get attention. It's scary and startling. Maybe that's your goal, but in that case couldn't you just say, "Hey, please don't come in here, because I wont like it and I'll be all mean to you, so just a heads up. Like this is my house, and I'm very protective of it, because my possessions mean a lot to me, because I haven't yet discovered the Buddhist notion of letting go of all worldly possessions. Thanks for listening." That would be so much nicer than continuous barking. Just a suggestion.
(flickr photo Picture 179 by Wyscan; http://www.flickr.com/photos/wyscan/1055227371/)