Yoga sounds great, you just have to find something you love. If you don't it's really hard to stick to. Maybe you need to find another yoga tape that appeals to you. I have a lot of tapes and this one is the only one I really enjoy. It also makes my back feel great and I feel so much more relaxed so there is the added benefit that I think got me past the first two sessions and into the second week.
Walking is a great exercise, I would never make it as a runner. Glad to hear that you are thinking of adding to it. It is true (though I can't believe I'm saying it) exercise is addictive.

Jo-Ann