I find it exceptionally easy to get to and from HH from any part of the resort --- almost no waiting because you can get on the first bus that arrives at the bus stop. Just verify with the driver that they will stop at the HH ..... there have been times that the bus was full and a driver tried to whiz by the HH.
To return, it's quickest to walk across the road (by the boat dock) 2 minutes to the first bus stop, Penninsular Road, and jump on the first bus that comes. If you're in the Miller's Road area, it may be quicker to walk than ride the bus around, but there's a choice.
I honestly don't know the status of the "Internal" bus. I used to see them occasionally, but rarely noticed them in the last few trips. My guess is that you could be waiting for awhile at the HH entrance to catch one. It may just continually circle the property, but once in a while we've been waiting 15-20 minutes at a bus stop for a specific bus, and have rarely seen one go by.