I did this, my fogs come on with the key.
Cut the red/yellow wire on the fog light switch. Splice it into the black/yellow wire on the defroster switch. I took the cluster trim off to do it, some people say you don't have to do it. They also recommend to cut the red/yellow wire 2" from the fog light switch. Also tape up the end of the spliced wire so you don't have any shorts.