I had basically the same operation several years ago. Cycling has been about the only exercise I can stay with. All other exercises causes problems. Not sure how long to stay off. I did not discover cycling until a few years after the surgery. I was floundering with my lack of exercise due to back pain and was becoming depressed about my future. Once I discovered road biking everything changed. I am now in good physical condition, well good condition for being 64 years old. Last summer I routinely rode metric centuries in 3 hours or less. For me, that is great shape.

To sum it up, cycling after back surgery has been a life saver.