In Montgomery County you will find that crime is pretty pervasive throughout. See
here for a crime map. The vast majority of it is property crime. The risk tends to be higher in easily accessible areas with high population densities (see Lake Forest Mall on the map below). You might find one area has 1/3 or 1/2 the crime per capita as another, but you'd be fooling yourself to think that you can find a place where you won't encounter it. In the past 1.5 years, we've had one attempted break in. The guy ran away instantly once my wife screamed. There was one other attempted break in on our street in the same time period. We are getting a security system.
The reason for this is that Montgomery County is very friendly to its low income residents. There's a lot of subsidized housing and its spread throughout the region pretty evenly. This tends to invite a lot of property crime.
Violent crime in Montgomery County, however is very low. In 2008 there were 18 homicides which is about the same as the count for 2007. (See
here) . This is in a county of nearly 1 million people. This is less than half the national average of 42.802 homicides per 1000000 (see
here).
That all being said, I doubt you will find a "nice quiet safe city" in Montgomery County if you think attempted break in does not equal safe to you. Your best bet is to look elsewhere.
There are other reasons to live in Montgomery County, however, such as: diversity, great schools (even the "bad" ones), proximity to job, proximity to DC/metro, good planning relative to NoVA, well-established neighborhoods.
We enjoy living in Montgomery county and take the good with the bad. You'll have to make the decision for yourself, however.