Hello Fellow Bay Area resident!
It is not a good walk.
You CAN walk to Mk from WL, but it is along a heavily traveled road with busses, cars, etc. I'm sure it has been done, but you should stick to a bus or the boat to MK.
One afternoon we walked from Poly to WL, although not a long walk, just a ton of bus traffic! Just seemed like we were begging to get hit!
Do yourself a favor and take Disney Transportation. Now, you can take a boat to Contemporary and walk to MK from there, if you're dead set on walking!
Have fun!