My sense is it’s an adult spider simply because it built a nice web and is open for business. But I think baby spiders are pretty much on their own when they hatch, so they would have to start web building pretty quick. I also googled baby spiders with no luck.
It didn’t make a move while I took these shots. The web was anchored between the arm of a patio chair and a bistro table. I was able to shoot from a few inches away. I left the spider alone Later I noticed the web was gone, and it hasn’t returned. Evidently it wasn’t a very fruitful feeding ground.
To cover all bases, I also googled orb webs. The reinforced center bulls-eye seemed like something I could track down, but I struck out on that count too.