I think pets are a good idea for families anyway. I grew up with a collie-labrador mix who was really great with all of us kids but very protective regarding strangers. She would play softball with us and also keep watch.

But many of the cats are also very territorial. My aunt had a pair of cats that alerted her to a prowler by hissing at him through the window, and they scared him away.

Now that I live in an urban apartment, I chose one that is in a more private location in the building, and definitely not on the first floor. I also keep all of my japanese weapons in the bedroom. But even though my neighborhood has gone through some good and bad times, no one has ever bothered me. Maybe they know not to!
Be nice, until it's time to not be nice.