Sometimes sites require you to indicate the Bundesland or province inwhich Konstanz is located, this is: Baden-Württemberg.
Also very useful is the Google Map with the conference campus(A, Universität Konstanz) and list of hotels in or near Konstanz.For this map you can clickhere.
There are a couple of budget hotels in Konstanz. These are notspecifically categorized in the tourist information site of Konstanz.
Under online booking the participant can key in the maximumrates, say 50 Euro (or whichever applicable rate) and the list ofhotels offering rates in that range will be shown.