Like Jim said, I would remove the door panel, locate the two nuts that are welded in place, and stick a punch through each hole to create little pimples on the outside door skin.
BTW, this question has been asked before and the punch that's most often recommended is one of those
automatic center punches that you can find at any hardware store, or even Amazon. You won't have to swing a hammer in a confined space if you use an automatic punch.
When drilling, I recommend starting with a small bit and work your way up to the size you need to fit the screws through the holes.
http://www.amazon.com/TEKTON-6580-Automati...h+spring+loaded