Think outside the box. You're not chained to the pattern. You don't have to do it exactly as written. If you want to add a ribbed border, do it. You can also do a provisional cast on for this, put those live stitches on the needle later, and knit downward with either a rib, straight garter, or a seed stitch border. But I think it's just easier to add the border first and go upwards until you start the cable pattern.
I don't understand why they would want to start with a turning row anyway. The cast on stitches are tight enough, and the turning row is tight so it would be extremely difficult to do. If you want to do the pattern as written, I don't see any reason why you couldn't do a regular long tail cast on and just knit the first row around, then start the pattern turning row on the second round. It would be a lot looser to work with.