Is there a bus service available near Casa Borboleta?

Yes, there is a bus from the village (Pedreira) into Silves itself, which is the line 31. This bus route is operated by VAMUS and runs daily, including holidays. From Silves, you can connect with various lines, taking you throughout the Algarve. The train station is just outside Silves, and is best accessed by taxi (10 minutes drive). Here is a link to the bus timetable: https://www.vamusalgarve.pt