There is no meeting point. The self-guided audio tour is designed to start at the Volta do Duche. The easiest way to get there is by reaching the Largo C.M.Sintra bus stop (2710-631 Sintra, Portugal) and you’ll be at the right place to start the tour.
The tour ends at the Palace of Seteais (R. Barbosa du Bocage 8, 2710-517 Sintra, Portugal).