I have never seen a sign, but I have been asked to leave the moment I entered a restaurant once. I live in a rural area and honestly people aren't as used to foreigners as they are in the big cities. I feel a huge difference in how people behave around me when I go to one of the bigger cities.

On the other side of things, the friendliest people I've ever met were in a town smaller than mine. I had made some bad travel plans (also called not doing any research and just went) and I was stuck in a tiny town for a day. I've never met nicer people anywhere!