Even when you think of a Sword & Sorcery campaign as a series of disconnected adventures, I was still unable to find anything anywhere on how to actually set up individual Sword & Sorcery adventures either.
The players should be free to do whatever the hell they want. I think the task of the GM is to provide them with stuff they can interact with.I also think that your ideas of helping/interacting with the locals don't scream S&S. Your PCs should be heading straight to rescue their friend (or loot his gear) from whatever the threat is. Anyway, in most S&S fiction, I think commoners who are on the run would be very leery of accepting help from strangers.