Nice. Warm enough to walk to your car a couple blocks or more...
Dress warm enough to get to your car but nice, like going to a good steak house.
Warm for nights in San Jose
Casual is fine.
I would say that it is definitely an opportunity to dress up.
Fancy attire is not required. Elegant casual is great if you want to make it a dress up night, but even dark blue jeans and a sweater is totally acceptable. I usually wear dark jeans and boots with a blouse.
Take a sweater. Check weather report before going.
Opportunity to dress up but casual is totally fine. It does get cold around the area at night, so bring jacket/sweater if the temp is in the lower side.
Anything goes.
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