When the party enters the villa, start a progress bar with 6 boxes for the bandits. Whenever the party makes loud noises, mark 1 box. You can mark 2 if they made a real ruckus.

Upon reaching 4 marks, the bandits will be alert enough that when the party reaches their lair in Inside - South > Exedra, they will be awake and prepared for them. If the bar fills up (6 marks), the bandits are alerted enough to expect armed intruders and have not just readied themselves, but also taken defensive positions. The party will begin the combat with the bandits in a desperate position.