Although Bernal is known as being somewhat safer than say the Mission, it is not like living in the burbs.
Here the facts, as I gather them from crimemapping.com (you can check it out--just put in your address and it will give you crime stats within a radius of that location):
There have been no murders this year in the immediate area of Leese and Crescent.
There have, however, in the past 6 months been a lot of assualts in Bernal Heights, including a block away on the corner of Mission and Crescent (Mission gets a lot of assaults). These took place in the afternoon not night.
There have also been strong armed robberies in the area in the last two months--both took place right in the middle of the day (11 am and 1 pm respectively).
Point with all this is not you should not live here, but that you need to treat it like living anywhere else in the city: be aware of your surroundings, avoid situations where you increase your chances of something bad happening. If you are a young female or a guy who looks like an easy mark, I would not take BART at night. If you are a pretty well built guy, who is in shape, and stay aware, you should be okay. Always move quickly and stay aware.
Okay, good luck!
