How should you dress to come here? Is it shorts & flip-flops style, or does it lean towards upscale?

You can't go wrong with either attire. Depends on if it's day/evening. I'd say business casual would be as far as it would go on the attire.

Casual would be just fine. Especially outside.

I was in a sundress & flip flops when I went. It is mostly outside.

I'd say smart street upscale