Ken, I have a corn snake right now that before I got her, she had eaten nothing but live, ever since she was a hatchling... She ate the first F/T offered to her with no problem. Just make sure they are really hot, and sometimes you need to do the zombie mouse dance.
Another note, I have had a couple of wild snakes as well switch over to F/T mice right away as well. In fact, my Gopher snake is the one snake I have that is very soft mouthed when it comes to feeding, today he slowly took the mouse out of my hand, it was very interesting. I was expecting him to be a hard striker, but not in the least.