One hears different stories what concerns the security of the neighbourhood UChigago is situated in...Are these all rumours ore partially true? Any information, particularily from people attending UChigago, is highly appreciated! Thx!

Most of these stories relate to a time about 10/20 years ago, when Hyde Park was on the brink of slipping. However, especially in the last years, both the University and the City of Chicago did a lot to change things. Personally, I do not feel insecure. My impression is that many rumors and stories result from the US-american way of panicking and exaggeration. As soon as something is going on - and this is a big city after all - there are mass-emails and "security alerts" everywhere. This gives a feeling of being insecure although I never experienced a situation which I would consider as close to problematic.
Another factor possibly contributing to the stories is that the law school is on 60th street and that an area with many problems begins three streets further down south. However, this means only that one should not go there. But this is true for many other University locations as well, just think of Columbia (and I heard interesting stories about Cambridge (Harvard), but I can't comment on these).
Additionally, the University provides a lot of services, especially for women. As far as I know, there is an agreement of the University with the police that you may call a police car when you are going out late. The car will follow you then until you are home safe.