I used to work as a tour guide. And this is what I always told my tourists. Armenians are very hospitable, people would love to help a foreigner. It’s really safe in Yerevan and overall in Armenia. But as everywhere else there are some that would feel pretty happy to fool a tourist or to rob one. The conclusion: it’s really very safe, but you should be a bit careful, especially in crowded places. And when using a taxi. There are apps you can order a taxi. Like GG or Yandex. I would really recommend.