In general, the farther north you go, the better Peru’s beaches are. This region includes some truly incredible archeological sites, like Chan Chan and Huaca Rajada where the Lord of Sipán was found.
It also has the westernmost point of South America. Just south of the town of Talara is a little beach community called Negritos. Follow the coast south to Playa Balcones and you’ll be as far west as you can be and still be on the South American continent.
There are many options for busses going north from Lima to this region. The best airport in the area is Piura, with several flights daily from Lima.