Alarm Security signs posted on your door and in your yard does scare off some burglars but not all burglars.
Some burglars are willing to take the chance at breaking into a home even when security signage is clearly posted as some know that not everyone has a security system in place even though they may have the security sign posted.
But it is a good idea to have security signage on your home and in your yard stating the place is being watched by camera and a security system is in place.
Actually having a security camera system and security alarm system in place is a better option if you can afford to do so but if not then the security stickers and security signage can help make your home less attractive to burglars.
Burglars look for easy homes to enter and target and don't want to risk being caught so the harder it is for the burglar to get in the less likely your home is to be broken into.