Capri

Donna, YES, you can absolutely get to Capri from Positano. Walk down to the dock and buy a ticket at one of the small booths there. Walk to the end of the concrete jetty and board the boat. As I recall, the trip is about an hour. You'll arrive at Marina Grande and will then have to take the Funicular or one of the distinctive open top Taxi's up the to the town. Be sure to note the times of the boats back to Positano. If you find that the Funicular is terribly crowded when you're trying to get back to Marina Grande, I'd suggest going by Taxi and avoiding the crowds. Happy travels!

Depends when in October. End of the ferry season from/to Positano can be a moveable feast. The last couple of years it has been about mid October officially but sometimes there is the odd unscheduled sailing after then. You will need to check when you get there. Crossings between Sorrento and Capri run, weather permitting, year round.