I called on a Saturday morning and luckily there was one cabina available for my mother and I, who drove down from San Jose. We found Encantada an enchanting place off the beaten track right on the beach in Esterillos Este. After arriving, the afternoon was spent on the beach taking a long walk, trying out the hammocks, and sourcing locally caught fish for a magnificent potluck-style dinner hosted by Diana and Mikey and a couple friends of theirs down from the U.S.
We didn't partake in any of the tours but I'm sure if we had it would have been helpfully arranged. Instead, we spent the following morning lounging on the beach--relatively unpopulated after the hordes of Jaco--quietly reading by the pool, and enjoying fresh fruit and coffee for breakfast.
The accommodation itself is a bit utilitarian and the hot water was non-existent (fine if you're just rinsing after getting out of the ocean), but altogether grand for us, who've done a lot of both high-end and budget traveling and who feel that personal service in the form of welcoming hosts to be one of the best signifier of quality.
Thanks to Diana and Mikey, who really made our stay at Encantada super relaxed and very welcoming!