Don't miss the fish market (turn left out of the port, walk 1/2 mile past a thousand fascinating market stalls). Lots of very affordable independent tours at the dockside. Probably the best value trip we have ever taken. 6 hour van ride to scenic Lake District for $30. Also, be sure to buy local wine and/or Pisco sour at the stall where you get back on the tender!
Take advantage of the ship tours to make good use of the day before your flight home! Check your bags on board and do not see them again until you get to the airport! Absolutely the best way to disembark!