As a solo female traveler, Plauen is perceived to be very safe. The city is generally very calm and has a low crime rate, especially against tourists. Public transportation and walking during the daytime is secure, and the evening hours are generally safe as well, so long as one sticks to well-lighted, populated places. As everywhere, it's important to stay alert and attuned to your surroundings. Germans are generally helpful, and most locals will be more than willing to help you out if you need directions or assistance.