As I plan my spring/summer purchases, I want to buy things that I can take on a mid-summer trip to California wine country. I've heard it's kind of a smart casual "dress code" - and that I need to wear comfy walking shoes. I plan to bring layers because the evenings get fairly cool, but the days are very hot.

Is it appropriate to wear:

* somewhat casual summer dresses - sleeveless and sundresses?
* dressier shorts?
* casual skirts?
* Can I dress similarly for the restaurants in the evening?
* any other tips/recommendations on clothing & accessories?

This trip will be a celebration of a big birthday for my husband, and I want to look sharp. Thanks so much in advance for any advice you can give.