Anytime. I live here year round. If you come in November, December, January and February may be all the way to May be ready to sweat very seriously. Temperatures are high. You may have the feeling that you might be cooked alive. May is the month when our winter comes into place. Thinking mythologically, God (Ñamandu) created the world and himself in the dark night of winter while he sat in the middle of the original winds. Original Winds is nearly synonym of winter. Temperatures drop and there are quite a few rainy days with very cold rains. If you don't mind that's OK.
What to bring?
We only have two very clear seasons: summer and winter. Winter may be cold and rainy. Be prepared for cold weather, hot weather, wet weather all in the same day maily from May through August. In the summer, a hat is needed, light clothes are a good idea. I will come back with more....
I'm working on this