Hi, I have spent a lot of time in San Fransisco both working as a student a good few years ago, and now visiting family and relatives there with my own family. The last time I went to Haight Ashbury it was seedy and grotty - it had its hey day in the Hippie era and it is now, in my opinion, just full of ageing hippies and junk shops, and not very safe at night time. I stayed in a hotel in the Fishermans Wharf area last time which was fine and safe at night. The Marina district is a nice district, and Sunset is fine too. Avoid the Oakland area, its not very safe or very nice. Parts of the Mission district are quite dodgy too. Suasilito, which is across the bay is really beautiful. Avoid the Tenderloin district - its also rough and seedy. The area around Nob Hill is also lovely but probably quite expensive. North Beach is a great area - full of great restaurants and bars and clubs and would be a good place to base yourself. I have not found it dangerous or threatening at night time but like any big city you need to be careful. Hope this is of some use to you. You will love SF.