Just wanted to share some personal experience about some banners we purchased. We had the luck have having an awesome "Tinker's Station" sign out front when we bought our property, though there was no indication of what we were going to do. We decided to get two banners telling the world we were making a hostel and giving our web address and our internet traffic spiked a couple of hundred hits for the next few days!
Obviously this might not sound like much for some of the bigger hostels, but for a small little startup in a town of 100, it felt pretty good. Here's a few pictures of the banners (covered in a bit of snow):