No, it isn't possible. You can take a bus anywhere and transfer to an OKW bus or take the boat to DTD and transfer to the OKW boat (it docks near the balloon launch site and not near the Rainforest Cafe). Disney Security will not allow guests to walk along side the roadways in WDW. And that is what you would have to do (or walk through a backstage area and that is not permitted).
No. Just checked Google maps and there are no sidewalks or pathways. Boat is probably the fastest way. Or should I say least slow. I would think you're looking at at least one hour total travel time.