I'm an American living in Italy and I'm new to touring, but I know the area you're passing through pretty well and I'm envious. I'm taking some time this summer to tour central and Southern Germany; hopefully you can pass some of your hard earned wisdom on to me.
Brains is right, accommodations shouldn't be hard to come by. One thing I've noticed is that if you go to a campground that is near a village/town, more than likely there will be houses nearby that are also renting rooms, just keep an eye out. I found a very nice (very cheap) room this way just north of Plocken Pass (sp?) on the Italian/Austrian boarder west of Villach.
When you're in Salzburg I have the hotel for you. It is called hotel Zistelalm and it is south west of the city near the top of this BIG HILL. It only takes about 30 minutes to get into downtown Salzburg, but the other way may take you closer to an hour. I'm weak, it took me more than an hour. By the way, nice hotels are always up at the top of hills and the really nice, really cheap hotels with bar maids that flirt with you are at the top of mountains and the only way to get to them is by long cobblestone streets. Anyway, here is their website. http://www.zistelalm.at/
It really isn't as swanky as the pictures look. The food is great, the view is wonderful, the people are nice, they have a good place for your bike so the cows won't steal it, they have a pool, and the rooms are decorated with antiques. Make sure you get the garlic soup.
Keep in touch.