We only had a problem one morning getting a bus, but only because it was 30 minutes late...and of course, it was the morning we had an early breakfast at Cinderella's Royal Table. Luckily concierge was able to notify them of the problem and we got right in when we got there, but we were late and just a little stressed!!! LOL.
Other than that one time, I found the transportation fine. DTD is a hike, but the other parks aren't terrible to get to, especially since it's a dedicated bus for AKL and makes no other stops.
As for walking to the AK, I don't think so, but then we never really tried it. Someone else may be able to answer this definitively for you.
Donna C.