It’s a bit overwhelming especially when you get bombarded with all information for the Northern Hemisphere but you live in the South. I agree with what Brianna said above.
Here’s a related topic: Celebrating Ostara in the Southern Hemisphere
I lived most of my life in South America and in my experience both ways are valid. Go out in Nature and experience Ostara, the best time of the year is coming! Your rituals will organically match those energies. However you can celebrate Mabon with us, “in spirit”, as if we were all in the same calendar. After all, we are all celebrating independently, together. 