One of my roadie buddies had a lumbar fusion. He was back riding within 3-4 months IIRC. Within a year got a new bike because he wanted a much more aggressive riding position than he'd been able to tolerate before the surgery. It was about two years before he felt he'd reached maximum recovery.

My dad is one year out from lumbar fusion. He got some relief from it, but he was really disappointed at first because he had had instant relief from the cervical fusion he'd had about 15 years earlier (maybe longer than that). I THINK he's glad now that he had the surgery, but it was at least three months before he felt he'd received any benefit at all - and one of the things that the surgery did was make him and his doctors realize that not all his symptoms are the result of nerve root compression. (In his case, neuropathy is a side effect of medication.) It's true he's older and in poor health, but he's actually quite active for his condition - he has a backpack that he uses to carry his oxygen tank on long walks, and while I wasn't present for most of his PT, that's the sort of thing he's usually very motivated about.

So ... YMMV. Good luck, whatever you decide.