I had a spinal fusion L5/S1 in 1996. I talked to 3 different doctors, picked the one I liked best, also was highly recommended. My surgery was a "Ray Cage" took bone graft off my hip bone.
6 months is likely not going to be the full time of limited activity, Mine took about a year to fully heal. That is what they told me too, but it was much longer. But you don't want to mess up an expensive surgery trying to do too much too soon.
Make sure you vet your doctor. get input from others that have done this, go online and do some research.
If they can go through your front/stomach adomenal (sp?) side instead of the back side it may be better. many people with fusions have pain from the scar tissue that develops putting pressure on the spinal nerves.
Other things to consider is that doing three levels of fusion will put more stress on the discs that are not damaged now.
I am glad I did mine, gave me a better life, but it is scary and the recovery is long. I wish you luck with your decision. If you want to talk to me call my office 360-693-1621 ask for dave g, I am on the Pacific coast.