It's the fifth largest city in Missouri making the demograghics very different. You can't judge from a report because everywhere is dfferent. Ask people that live there in the different areas, thats the best way to get an answer
When I lived there it was great, there are tons of bars and a ton of people ready to party. Its a great place for young singles or people still in the partying stage. I now have two kids and I am looking for a quite neighborhood to raise them in, so I am looking towards O'Fallon, St. Peters area.
Everyone's definition of "safe" is different. As Alicia has noted, checking the police reports and the crime stats is one way to answer the question. Another is to ask people who live there how they feel about their city. I know many 3rd and 4th generation families who wouldn't dream of living any where besides Florissant. If you want to know about an area, drive through it. Visit the shops and restaurants. Talk to the people who live there. Ask them how they feel about their city