Comments & ID Thoughts
Comparing with the other spiders on the site, this looks like a "Banded Garden Spider" (Argiope trifasciata). Since I'm not an expert, my guess could be totally wrong...
Significant web: diameter of at least 50cm, web attached between shrubs about 2m apart.
Significant spider size: I had nothing to measure, but seemed at least about 5cm leg span.