Hey Mike,
I recently got back from a 9 month backpacking trip in South America. I spent 3 months just in the North of Peru, primarily trekking around Huaraz in the Cordillera Blanca and Cordillera Huayhuash. It's amazing there!
I generally prefer the mountains to the beach but there are some nice spots on the coast if you're into surfing, like Huanchaco and Mancora.
In Peru I spent $17 USD/day (not including flights, vaccinations, or gear I bought before leaving home). That's staying in cheap hostels, camping a lot and mostly cooking or eating cheap local meals for 4-5 soles ~ $1.50 USD.
When are you making the trip down? Hope you enjoy it!