Some of the Worlds best street photographers only use 50mm lenses, it's "different strokes for different folks", if the OP has a 50mm lens use it, the widest lens I personally like for shooting street is a 35mm, I don't like anything wider, and there isn't an enormous difference between the 50mm and the 35 mm in the final results, and fast 50mm lenses that are usually at least f1.8 and sometimes f1.4 are a lot less expensive than fast wide angle lenses.