I may be coming in a little late to this discussion, but I have back issues too, and may be able to offer you a little help.
I've got double major scoliotic curvatures of the spine, with steel implants and spinal fusion through the entire thoracic column and partially in the lumbar column, too. My cervical vertebrae can move well enough, albeit with some rotational limitations, and I have 3 lumbar vertebra that are still able to move, although the top one below the rod/fusion end is heavily arthritic and is shaped like a mushroom.
I had the surgery when I was 18, and I'm 50 now. I know a thing or two about chronic back pain, but more importantly, I know what to do to minimize it.
Echoing what 3alarmer said, by all means do start yoga, and get an instructor that knows what they are doing and can tailor a program to suit your needs. Work on flexibility--upward-facing dog, downward-facing dog, cobra, various revolved angle poses, sun warrior pose, extended side angle pose, etc. Also, do lots of core work beyond what you do in yoga class--strength in your core as well as flexibility work will help a lot with chronic pain.
Too, what I'm finding in my search for a road bike is that "endurance geometry" or cyclocross road bikes tend to have a longer head tube and a slightly more upright position than most road bikes. Also, you may want to look at a frame that's the next size down from what you normally ride for your height. It may not seem like much, but even a few degrees less torso angle off perpendicular and a little shorter reach to the bars/hoods makes a world of difference.