I have an aunt in a wheelchair that trained one with a spray bottle of water. She would get their attention first and have her sit down...
She would then open the door slowly and while doing so telling her to "STAY", if she got up she would spray her.
She ran off the first few times but she practiced this for a few days and my aunt got her trianed to sit and stay everytime the door opened...
Not sure if you have a screened front door, that might help too
