Looks like you'll be there Friday 21st. Here is an idea you'll not see elsewhere. On Fridays at noon (be on time, it is popular with locals) the El Estadio restaurant on the Plaza San Martin has a buffet of authentic Peruvian food. About $10. They have a large selection (over 20 dishes) that I can attest are extremely well prepared. All delicious and quite an opportunity to try so many great classic Peruvian appetizers and entrees.