Bus travel from Piano Serrento to Sorrento?

Here is the summer bus timetable for Piano di Sorrento to Sorrento. Page 1 shows the return timetable. You could Google map P di S to try and see where the various stops are. I'm afraid I'm not familiar with that area, only journey through on my way to and from Sorrento

http://www.vesuviana.it/web/files/Linea8Ae.pdf

Don't rule out the Circumvesuviana train which runs 2-4 times per hour between the 2 towns. Trip takes only 5 minutes and avoids the traffic congestion that can sometimes occur. Cost is EUR 1.10, probably about the same as the bus.