Frequently! It takes about 25-30 minutes, less on the way back to the hotel if you're already in the Village. That's the most pleasant way to walk too - you cut through the Santa Fe car park and follow the canal until you get to the Village, it's much nicer than going all the way by the road.
It's lit all the way - and I've always felt safe, even after midnight, although I wouldn't walk it alone, only in a group. Once you've ridden the shuttle once you'll work out where to access the Santa Fe but I'll see if I can work out how to mark the route on a google map (might take a while as I'll have to ask my DD! )
The shuttle buses are very easy to find - once you exit the park they are right outside the railway station. The yellow ones are for the Disney hotels and the pink ones are for the offsites - you take #54 for the Explorers.