Yes, there are times when the butterflies come down by the thousands to the people right down to the parking areas and even lower. But there are times when they instead of taking this slope, they take the opposite one, in which case you can see them only if you climb. What makes them fly in the opposite direction? Winds, temperature, humidity and other natural factors. Can we predict their movement one or two days in advence? Totally unpredictable. Something important is to remember, as a repetitive visitor to this wonder,  that your moment with the butterflies, your visit to them, is not but an instant of a complex process that takes months, and in your next visit you wont see necesarilly the same you saw the first one. Therefore, we reccomend to go there, with the open mind that this time the butterflies might play with a different stratagem, and you could be forced to modify your own strategy.