Mark,
So the start of your trip will be fairly crowded, but as the week goes on you should see levels drop a bit. Even then it will certainly not be a "light" time of the year, but you should notice a pleasant easing of line wait times, bus wait times, etc. That's good news, right?!?
As for bus transportation, here is the rules you should follow;
- If you are going to a theme park, take the buses from your resort.
- If you are going to another resort (say, for a meal), take the bus to Downtown Disney and then to that destination resort.
There are a few exceptions to the second rule. For instance, if you are headed to a Magic Kingdom area resort on the monorail line (Contemporary, Polynesian, Grand Floridian), it can often be MUCH faster to take a bus to the Magic Kingdom, then the monorail to the respective resort.
But if you are not 100% sure, there are two things you can do. First, you could send me a question via my bio page with details on where you are going (and what time of day, i.e. for a breakfast, etc.). I would be glad to provide a specific suggestion. More valuable is to always ask the resort transportation desk cast member what you should do. They will know, on a case by case basis, what to do.
Have a magical vacation!