Are US dollars accepted in Peru?
Yes, you can buy with USD in most places as long as it is a one or a five-dollar bill. However, that is not always true. So when you get to Peru, change your dollars for the sol (nuevo sol) at a bank.
You can change at a money changer on the street corner if:
There is more than one changer there. That tells you it is a normal business corner for them.
You know first what the current exchange rate is (use the box in the upper right corner on this page).
Avoid money changers that are not in a business area.
ATM machines will give you your choice of Soles or Dollars. Using the sol makes things much easier but you will pay a small charge usually for the currency conversion.
We generally use a BCP machine but there are some that charge more and probably some that charge less.