It's not illegal to take pictures of anyhting in the public domain. You can take pictures of streets and shops all day long. But it is better to ask. good manners and less likely to be accosted..
If taking pictures of shops then I would suggest a poloriser filter.. you can get them for digital cameras that take filters ... a polorizer willl reduce the reflection from the window.. you will be able to take a pic of window and stock rather than of yourself and this side of street.
I recently sold spare ones for a digital camera I had... I have a large one for my DSLRs... I will have a bash as at a very loose end at the moment
haaa bless
