I did the fesival a few years ago with a severely injured quad. I was either on crutches or using a cane the entire time I was there, which was about 18 days or so. Are you camping or staying in town? I was camping in Town Park and navigating the campground was the most difficult part. The Planet does have a handicap entrance closer to the campground for easy access, though I only went down to the field for about 3 sets over the entire weekend. I watched most of them from Run a Muck. The festival field is flat, so it's really easy to navigate, and everyone is super cool. Any time I went to get in line for something (beer, merch, food, etc.), people would let me cut to the front so I wouldn't have to stay standing. If you are staying in town and don't want to walk to the festival every day, get on the galloping goose, the free bus service in Telluride. You can plan your visits based on their schedule. Just make sure you get on the right one or you may wind up in Mountain Village. But the most important thing to remember while being a cripple at Telluride is to avoid Hooch. He thinks it's funny to hit cripples in the bollocks with a full whiskey bottle and then sprint away so you can't retaliate.
Sugar they did away with the handicapped entrance a couple of years ago, but hopefully they will re-open it as there are many festivarians with mobility issues.