We hired a taxi in Quito for $70 to take us to Tambopaxi near Cotopaxi. When the taxi got to the park entrance around 16:00, we discovered it closed at 15:00 to taxis and normal vehicles. Our wonderfully compassionate taxi driver Guillermo talked to the guard, called Tambopaxi, and eventually arranged for a local driver to take us into the park for an additional $35. Whew. The road in the park is quote rough, so this was probably a good thing.