It is and it isn't, you can walk on the roads over there, but you can't access the park without a guide or paying for the tour.
To walk on the roads, you have to get a wrist band, which costs between 120 and 150 pesos. The gov't made the the tour operator there buy the bands in advance to collect their tax, that used to be 30 pesos per person.....I guess the gov't has to pay for that metro somehow