The tourism side of the Grupo Ecológico Sierra Gorda, the local organisation that fought for the biosphere reserve and still runs much of its conservation work. Their guides are federally accredited, and prices include transport, entries and the reserve fee. The pin is on Jalpan; their office is on Avenida La Presa.
Day trips go out from Jalpan into the reserve; the multi-day packages include "the best of the Sierra Gorda" over three days, a route through the Pueblos Mágicos, and escapes to Concá and over the state line to Edward James's surrealist garden at Xilitla. They also run school and corporate camps.
The WhatsApp number has a Toluca area code, but it is the one they publish on every page.