Hey hardball, check right behind your brake pedal, you'll see a rubber grommet in the firewall. A lot of members use this location to get into the truck. I did the same sort of research when installing my fogs. You can poke through the lower rubber, for the hood latch release and you can route a cable through there for your switch.
I agree with ncranchero on the relay aspect too, this way, you can keep all your fog light voltage out under the hood tucked away and just run your relay 12v source in the cab to a switch. There is also a nice storage spot between the fender/body and the battery on the drivers side to zip tie/store your relay and wiring.
When you run the wiring inside the cab through that grommet, use a snake, or coat hanger and poke it out through from the cab into the engine compartment. If you look right around/below the fuse box on the drivers side you should see it poking out (give yourself a good foot or so and you'll see it for sure), then just duct tape or electrical tape your relay wires and pull the snake back through into the cab.
Good luck dude, let us know how you make out!
