End of October is one of the times we holiday in Sorrento each year and the Amalfi Coast buses are still busy at that time. There does not seem to be any really quiet period during the day eg from early morning commuter period - then tourists setting out for the day - and last but not least school children going home at about noon to about 2pm.
You may wish to consider taking the "Coast to Coast" tourist service (link below) instead. They do take luggage and it costs more but although I have not used it myself, reports say it is more comfortable.
And yes you will have to change buses at Amalfi to get to Ravello but that is pretty painless.
http://www.sorrento.city-sightseeing.it/eng/percorsi.htm
Or, for 70 euro, you could book this door to door car service from Sorrento to Ravello
http://www.transferelax.com/our-services.html