I lived high in the central mountain range of Veraguas, Panama as a Peace Corps Volunteer. Membrillo season was my favorite, as the stews and tortillas would take on a rich and satisfying cheesy flavor. following are more details i can recall about this amazing fruit.... It was grown as a midstory tree between the upper canopy of nitrogen fixers and ojoche, and the understory of mostly cafe with some cacao. Here in the heavy shade, they produced abundant fruits for 1/2 months of the year. however at the CATIE institute in Costa Rica where a friend was living, the Membrillos produced for 8 months out of the year, as they were in full sun, and a few meters away from a pond.
In terms of preparation, i believe the fruit was peeled with a knife to remove the outer 2 layers (one visible and the second almost unoticeable, which is bitter) before boiling and discarding the water.