I apologise for the poor quality of the pictures; it was a bit too sunny, and I had to use the zoom (I didn't want to disturb the spider). I'm fairly certain that it's in the genus Argiope, just not quite sure of the species.
The genus is known locally as "signature spiders" (aranha-assinatura), but that's basically any spider doing that anti-bird web pattern. It's yellower than the pic implies, colours look a lot like A. bruennichi, but those side "lobes" are quite different.
Behaviour-wise it's surprisingly chill. It doesn't run away like brown recluses and wolf spiders do, nor threatens you like wandering spiders (all three are native here).
The web is clearly strong enough to slightly bend one of the kumquat's branches.
I also got a pic of the spider having a meal. Perhaps the "web bedroll" around the prey might be useful for ID.