Here in the Netherlands the problem is not in getting an AED on the site, but to find someone who can apply it. There are many people trained in using AED's and we here in the Netherlands possibly have the highest density of AED's, and although there is an elobrate system to call trained people to a person with a cardiac arrest, the problem is still in getting enough volunteers to join in. It is no use to have an AED within 200 meters from every house, if you don't have people who can apply them. AED's are not difficult to use, but in a case of emergencie, you need someone who can keep his/her head calm and follow the instructions.
The defibrillators I've seen give audio instructions plus have clear illustrations of how to use them. Unless the bystanders are REALLY stupid, it shouldn't be a problem