It all depends on what you are comfortable with. Be aware that it is air conditioned so a light jacket or sweater might be needed. Especially if it is cool outside the inside will be cooler.
Dressy casual. Some folks were quite fancy, others somewhat sporty.
Either is fine. I've gone in shorts and dressed up.
It's fine
You get a variety of apparel here from summer suits and dresses to shorts and polos. Both are fine as there is no dress code per say, just whatever you are comfortable in.
Casual is a better choice.
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