Manglaralto is the town just south of Montanita, in fact you can walk there along the beach in about 25 minutes.
No noise, about 3 roads parallel to the ocean, just like a coastal Ecuadorian town should be. The roosters in the morning are the biggest annoyance.
Theres not much surf here or other things to do besides lounge on the beach, but for most that will suffice.
Where to stay?
For a bare-bones good enough place you could try the Hotel Manglaralto with rates starting at $12 per person per night.
Or you could rent a tiki hut or house at Casa Blanca.