I suspect that almost anything goes. Having said that, you won't be refused admission, unless you are in a bathing suit. Suggest that you wear long pants (jeans or khakis) and tee-shirt or polo-type shirt. I am talking about lunch. At dinner, the attire is a little more dressy. That means jeans with a button-down shirt. Don't forget to have breakfast in the Fountain. It is just downstairs from the Polo Lounge. The breakfast is crazy/amazing. One long counter and people are dressed every which way. Everyone loves the Fountain at the Beverly Hills Hotel. Start with the fresh-squeezed orange juice. It just gets better from there. When you walk in, you can smell the waffles baking. Really a special little venue. Sometimes, I stop in at that Fountain when I am in the area just to get a good salad. The ambience is so great and so democratic. You can be the biggest celebrity in the world, but those seats are first-come, first-served.