i'm going, i already booked a backup hotel option but i'm still looking for somewhere... nice. evidently most places aren't releasing their availability for next summer for a while so it's making trying to plan difficult!
booking.com has a reasonable range of the b&bs and slightly larger hotels in the area.
your best bet might be vienna, salzburg doesn't seem to have a direct road route to the spielberg area. i think only easyjet, austrian and ba go into vienna but it's worth having a play with some indirect routes from where you are - try the major european national carriers instead of the budget airlines. swiss in particular do some really good pricing via zurich and geneva to loads of places around europe, and they're owned by lufthansa so they have access to a massive range of airports. british airways have a lot of flights to vienna and will obviously connect with airports more local to you too via heathrow.
if i were you i'd be considering a quick crafty trip to monza for the april season opener too. ok the support is rubbish, but it's pretty easy to organise within normal weekend hours and the fr3.5 races are exceptional