Choose a hotel in the city center of Lausanne. Bussigny and Crissier are suburbs and you will need a car to reach the Theater if you stay there. You can also check the Postal Code/ZIP code that should be between 1000 and 1018. Keep in mind that Lausanne is a small city and most of the hotels in the center provide easy access to the Theater. Bus lines 2 and 21 offer direct access to the Beaulieu Theater.
When you do book your room please specify that you are a Prix de Lausanne participant, as you may qualify for a special rate ;)