A Quick Thought on Focal Lengths in Street Photography

Generally, the more populous the area you are shooting in, the wider focal length you want. - Centre of London: 28mm.
- Krakow/outer London: 35mm - rural/ deserted streets: 50mm There are plenty of exceptions (some only use tele lenses. Some only wide. Also are street portraits street?) but I think this is a pretty good starting point.