There probably isn't a good route. When I've had to drill, I used a punch to mark from the passenger side. If you dimple the metal enough, it will be easy to see from the engine side, and to see if there is anything in the way before you drill.
I purchased a 3/4" hole drill designed for metal, and a drill extension from Ace hardware for under $15. It takes about 5 minutes to drill the hole. I use a grommet to protect the wire, and a little body putty to seal it up.