Mount Isabel de Torres is about 3,000 feet high.
You don't need any reservations, just go to the Cable Car place (on the way to Santiago right after you exit Puerto Plata on Highway 5 also known as Carretera Luperon).
The ride is quite interesting, though I haven't been on it in quite some time. The last time I was there you could still see some remnants on the mountain of an Airplane that had crashed onto it during a Cuban attempt invasion or something, I don't know if its still there. Anyways, nice ride up.
The views are outstanding. It is 3,000 feet, so the temps can be a good 10 to 20 degrees in Farenheit cooler than in the low lands. There is a nice but small botanical gardens up there, a smaller version of Christ the Redeemer, and a small suvenir shop.
QUESTION: Is the Teleferico open during night time? It must be interesting looking at the entire coast from up there like a christmas tree, flashing lights on and off by the neighborhood! Just wondering.