In many states, including Florida and Georgia,they have passed what is known as the "Castle Doctrine". You are no longer required to retreat from your position. Whether in your home or outside of your home, if someone attacks you with intent and a weapon and you fear for your life you have the right to shoot them. Several states have passed this law in the last couple of years since the Katrina fiasco.
From Wikipedia:
Castle Doctrine (also known as a Castle Law or a Defense of Habitation Law) is an American legal concept derived from English Common Law, which designates one's place of residence (or, in some states, any place legally occupied, such as one's car or place of work) as a place in which one enjoys protection from illegal trespassing and violent attack. It then goes on to give a person the legal right to use deadly force to defend that place (his/her "castle"), and/or any other innocent persons legally inside it, from violent attack or an intrusion which may lead to violent attack. In a legal context, therefore, use of deadly force which actually results in death may be defended as justifiable homicide under the Castle Doctrine