Nice report, Tony. Nature Air does a good job. As someone who lives in San Jose, I liked it better when they had all their operations in their own little airport, Tobías Bolaños (code = SYQ), on the far west side of the city. Now it means trekking all the way out to SJO in Alajuela.
Both Nature Air and Sansa, the other domestic airline, recommend against doing what you did, though. You're definitely on your own for same-day domestic-to-international and international-to-domestic itineraries, and they advise against it. With no joint ticketing or codeshares or bag transfers with the international airlines, you're not protected.
Glad you had a good trip!
