More recently, twice now I have had someone ring the doorbell (after dark) and then step back off the stoop and into the shadows. If I can't see a face through the peep-hole, I don't even acknowledge-the dogs usually do enough of that for me. After one of these encounters,I typically send the barkiest dog out back to raise a ruckus as well.
The few times I have been caught with the interior door already open and I go to the screen door, i've not discouraged the dogs from doing their Cujo imitations: slamming into the door and slinging spit. This tends to make most folks not want me to open the door.
Tass