I actually wanted to stay for two or three nights, at the end I spent 8 days there! The place is AMAZING, you camp directly at the beach (which by the way is super clean and just wonderful, as well as the sea). The toilets and the shower are very clean, you can cook and also put your things in the bodega. The owners are very friendly and helpful, gave me kitchen utensils and were always there if I got a question.
In San Agustín are just a few cabañas to rent, there are no big hotels and hostels. You've got a lot of restaurants nearby and some tiendas.
Highly recommended place to stay for 200 pesos/night (van) or 150 pesos/night (tent).
Blog: Lea M
Location: 15.69041, -96.23703