The city of Berkeley is a left wing nuthouse full of drug addicts, homeless people and liberals. In the 1980's Ronald Reagan cut government spending on mental health-care and in doing so ended up releasing vast numbers of people who lived in group homes and psychiatric hospitals on to the general public. To make a long story short the population of Berkeley doubled shortly after. Berkeley is now full of homeless people most with mental or drug problems but I would say 99% of them are completely harmless. There are some sketchy people who hang out around campus usually they are not from the neighborhood. It is a very safe city during the day but at night there are some very sketchy youths who come from close by areas such as Oakland and Richmond and try to get in to CAL parties. Two of my friends there have been jumped before and I have heard of robberies at gun or knife point but they are rare. The campus is in a nice part of Berkeley and unlike some colleges the buildings and houses are completely integrated into the city. Overall it is a really cool area to hang out and CAL football games create a great atmosphere. Berkeley is a safe city but like all cities it helps to know the areas to avoid during late night hours.
The city and college are very diverse with people of all religions, ethnicities, and races mixing so it is easy to find people who you can feel comfortable with. There are also vastly different groups of people so depending upon what you are into sports, computer games, studying, drugs, parties whatever you can find people who are like you