I work for one of the largest residential and commercial security system installation/monitoring companies in the world. My job is false alarm reduction, and working with City/County Municipal Codes and Ordinances. My wife and I wouldnt live in a house without one, and a dog. I think the presence of signs and stickers are the first deterrent. The second would be to be aware that when doors, garage bays, windows, blinds...etc., are open, your belongings are visible. I'm not saying keep locked up like fort knox, but be conscious of what people can see from the street. Dont give a crook a reason to pay a visit.
As far as a security system for your home, one place to start is your local PD or Sheriff's office.
Walk in, and talk to someone. Many cities have Municipal Codes, or Alarm Ordinances, which can have a major effect on response time. If they do have an ordinance, response time and number of alarm responses from year to year is public knowledge (this is good and bad). So, go in, and ask them... "if the alarm is going off right now at my house, there is a full moon, and its a friday night around closing time, how long is it going to be before someone is at my house? Seattle, publicly states average response time is 45 minutes. For the majority this is not acceptable. So most realize a security system wont completely stop crime, but it will lower your chances. Ask them if alarm registration is required. Many municipalities will not respond to home alarms unless you buy them coffee and donuts each year. Find out all you can from the PD/sheriff.
Know your neighbors. The good ones and the bad ones. Find out who stays home all day. Who works late. Who the nosey ones are, you know, the ones peering out the windows anytime a car goes buy. They can be an asset when noticing things are out of the ordinary. I recently found out, at a holiday "beer-bonfire" at a neighbors house, that there are 6 cops in my neighborhood, and 2 of them are on my street. I handed them beers.
Personally, the greatest benefit for us is the fire protection. If someone is going to break-in, they'll steal stuff that can be readily replaced. Electronics, jewelery, etc. If there happens to be a fire, and you have no monitored smoke/heat detectors, how long will it be before one of your neighbors notices your house is on fire? By then its too late. If a fire takes place, nearly everything is destroyed and has to be replaced. Now, think of everything you have that cannot be replaced if its destroyed by a fire. Most of these items have no value to a burglar.
I dont want to experience either, but i'd take a burglary over a fire anyday.
Get a security system. Teach your family to use it. Use it every day. Keep your contact information updated with the monitoring company. Get a maintenance agreement (much cheaper in the long run, especially if you run iton a faulty device and you are subject to any false alarm fines from the PD) and service your sytem every 2 years.