We will be doing a day trip to Siena from Florence likely on a Sunday. Are there plenty of buses back and forth on that day? Is this the best way to get to siena
You want the SITA bus. Here's a SITA SCHEDULE. There's a express bus to and from Siena. The main depot for the SITA buses are just over a block away from the main Florence SMN train station. From the track #1 side of the train station, go across the large main street and continue down the left side street for about 300 feet. The RS Florence & Tuscany 2005 book has a map on the second and third page. The SITA bus terminal is No. 32 on the map. I hope its the same in later editions.
My SITA schedule is a few years old, but it shows that far fewer buses run on Sunday than the other days of the week (e.g. only 2 express buses). Best bet would be to stop at the SITA ticket office a day or two before and ask about Sunday times. That would help determine whether you could do a Sunday bus trip that met your needs. Another idea would be to check the Sunday train schedules between Siena and Florence on www.trenitalia.it. Buses are usually more convenient, but maybe not on a Sunday.
james, Here is the schedule http://www.sitabus.it/sita-toscana/Firenze-Siena07.pdf