I'd think twice about posting a warning about being armed and ready to use it.
Some prosecutors has made a career by convincing a jury that you intended to kill someone and couldn't wait for the burglary to happen.
Most sane states don't allow killing someone for theft unless you're unfortunate enough to live in one of those states with a "stand your ground" law on the books. Nowadays that castle law is being taken to extremes.
Personally, I like the look of cameras and lights to deter common criminals. It's the uncommon criminal who will successfully rob you and you won't know it happened until you enter your home.
All the best,
Nonoise