It seems like the easiest way to tell whether books are welcome at various places would be to pay attention to whether others bring books (and keep an eye on the rest of the group to see how many rolling eyeballs).
I would think a place that provided a stand would probably have it for using..not purely decorative.

IF you're using a book, be sure to remember that they baffle sound. In front of your face, your voice is murfled and it's not much better when it's in front of an instrument.