I was scanning for unanswered questions, & saw your post from five weeks ago. I suppose there aren't any readers with your recent experience scanning the forum at this time, but I've seen a few stories over the years. How long you have to wait for exercise is going to depend on how much impact your doctor thinks you can handle, within what timeframe. I would not accept any generalizations when your spine is at stake. Get a professional prognosis from somebody with sports-med experience.
As you found, one of the problems with surgery is the heavy use of antibiotics, which can eliminate enough intestinal flora to cause constipation. Here is a sobering discussion of this problem, which cannot be solved as easily as it seems....
Meanwhile, you may enjoy reading some comments on a "Doctors" TV show that featured a type of therapeutic footwear developed for handling recoveries like yours. I own a pair myself, and their reduction of impact force helped me get over an achilles injury. They are also popular among spine surgery patients, although their design assumes a certain amount of ankle strength. Your problem is going to be having fewer disks to absorb the impact of running, and some adjustments to your footwear, running surface, and training regimen are likely to be needed.