Hostel life is all free and easy until you are on the bottom bunk and start to hear the sounds of two humans mating above you on the top bunk. This is perhaps not the level of immersion in nature that you were expecting, but I suppose it's good to know that everyone is having fun and getting along.
I took the short trip up to Playa Maderas for the better beaches and more mellow (read: old person) scene than San Juan del Sur. The beach was indeed beautiful and less crowded, and there were giant sand dollars floating around the waters. The hostel I stayed in was more like a nice hotel (except that generally in nice hotels people aren't getting it on in the same room as you), which provided a quiet escape from the party vibes of San Juan del Sur, but it felt a little isolating for me since it was a separate resort, and I hadn't been in San Juan long enough to be affected by those vibes. After two nights, I was ready to go back down south to the beach town, but I enjoyed the hostel's offering yoga (and letting me teach it for a free meal!) and having a movie theater.