Thanks for all the great responses! The table runner I did was a pinwheel pattern, so when I quilted it, I just sewed inside the seems about a quarter of an inch and it seemed to work well. The Rail Fence pattern would be hard to quilt with stitch in the ditch because there are no uninterrupted vertical seam lines.... only horizontal. That doesn't mean that I still couldn't do straight line quilting, I'd just have to go over places where there wasn't a seam.
I have practiced free motion before on smaller sample quilt sandwiches that I made just for that purpose, so I'm not unfamiliar with the process.... I'm not that good at it yet either though and don't want to ruin this big quilt after putting so much time into it.
I've never seen any tips or advice on quilting over/through the borders, so I'm still a little confused as to how to do it.... When I quilted the table runner, I just didn't quilt the borders at all. I thought about just running a decorative stitch straight down the middle of the borders, but again I don't know if it is safe to use the walking foot with anything but a straight stitch.... the needle bar is what makes the walking foot work, and the needle bar moves left and right with the needle during decorative stitching and the part of the walking foot that attaches to the needle bar does not move from side to side, so I can't understand how it would be possible to do that without damaging something.
Thanks again fro all the responses.... if I get anywhere, I'll post a picture
)