Yes there are, but by these days arrival is just beginning and the nuclei of butterflies in between the trees are yet very unstable. That´s the reason why biologists in charge of the sanctuaries, in coordination with the owners of the woods, authorize tourists visits from November 15th to 20th on, depending on the year.
Earliest we have gone is November 4th of 2006, and found several trees already covered with the butterflies. Nevertheless, by this days they are very dynamic, and they move constantly erasing rapidly the nucleus or so called colonies. But speaking of Nature, nothing gives you the warranty that it should be like this again next year.