There is a long twisting, one lane road leading into Typhoon Lagoon. I wouldn't think this would be safe to walk on. Also, you must cross an extremely busy highway, so I would say no, walking would not be a good idea.
You could take the SSR bus and then walk from there. There is a pathway around the lake from SSR, or a boat launch, but I am not sure how often that runs or when it starts during the day.
Make sure you ask before you stay on a bus. Most of the busses in Disney are not dedicated routes, they change destinations on every run according to demand. I would suggest going to one of the resorts closer to DTD to change busses or you could even take a taxi from TL.