Oh, I see this has switched to dogs. Well, 99% of people are incapable of handling a protection trained dog. 99.999% of people are incapable of properly training one. 99.99999% of dogs are not mentally able to be one. Buying an already trained protection dog is pricey. You can also be charged with assault with a deadly weapon if your dog bites someone, as they are trained to do it at more psi than an untrained dog.
That being said, I love schutzhund and French Ring dogs.
You can train any dog a fake 'watch' command, which in schutzhund is to snap and snarl and act aggressive towards a potential threat without biting. If a dog knows the command 'speak', get some friends to come over, put your dog on a leash, and have them stand at a distance. Say 'Watch!' and have your friends ask him/her to speak. When he/she does, praise. They key is getting them to bark not facing you... it's almost impossible to teach without a target. With a friendly dog, he/she'll be 'watching' and barkbarkbarking, but the tail will be wagging and it will be a deterrent more than anything.
Overall, I think maybe you should start going places either armed or with a friend.