I have a slightly different money exchange problem: I'll be travelling around Peru, with my last stop Puerto Maldonado before flying to LIM and leaving the country. I think it's going to be hard to get to zero soles before arriving in LIM. If I want to change them back to dollars, what are my options, and how bad will the exchange rate/commission be? Obviously, the more I'd be fleeced at LIM, the more careful I'll be in not accumulating unneeded soles.

Also, I am leaving Peru on a Sunday. I assume that even if I could get to a bank in Puerto Maldonado before heading to the airport, the bank would be closed on Sundays? And I assume it's not a particularly easy transaction to buy dollars at an ordinary Peruvian bank?

Finally, within the Peruvian tourist industry, how easy is it to just pay in dollars for transport and such? I assume the further you get from the beaten tourist track, it is harder? And that you'd wind up paying more if you don't pay in soles?