I didn't have a lumbar fusion, but have had two microdiscectomies. The first one was in July of 2012 on L4-L5. I was a mess after that surgery, pain persisted for 4-5 months. During those months I was getting A.R.T treatment and working on glute strength. I had not been lifting prior to this surgery, and they were extremely weak. I eventually got myself pain free and stayed that way until July of the following year, when L3-L4 got worse while deadlifting. I had the second surgery in September of 2013 and woke up from that surgery 100% pain free. I walked a little over 2 miles the same day. I started doing bodyweight glute bridges and ab wheeling (extremely short range of motion on those) about a week after the surgery and just kept building from there. I'm currently stronger than I've ever been and still free of sciatica.
My neighbor had a fusion done around the same time as my first surgery, and he was back to work powerwashing and doing yard work within a few months of his surgery. I don't know any other specifics, only that his scar is way bigger than mine.
I know how much the pain sucks, it will get better though. I wish you a speedy and painless recovery.