DUB shoes on, unless asked. If you have flat, rubber-soled shoes, you probably won't be asked. However, watch for people in front who are either wearing high-heel boots and have trouble balancing, or tourists, who assume is shoes off, and take them off needlessly, causing a ripple effect. And, the staff only tell them when they have them off
Gentlemen, flat rubber-soled shoes don't always get you through - if they look even a tiny bit 'clumpy' or boot-like, its shoes off.