My general assumption is that you are either a road vehicle or a two-wheeled pedestrian. If you are a road vehicle you follow road signs. If you are a wheeled pedestrian signs are more optional but you should be on the sidewalk peddling at walking speeds. The most dangerous times are when you are either transitioning from one to the other (say the MUP is also a sidewalk that ends suddenly dumping you on the road) or when you are acting like a pedestrian in the road or biking fast down a sidewalk.
If you are in the road and it says "road closed" then to you, its closed.