For street shooting I would absolutely use a flexible 400 speed film like Fuji Neopan 400, Ilford HP5+, or Kodak Tri-X 400. I shoot at ISO 400 often even when it's very bright out for street shooting so that I can stop down to about f8-f16 and have my focus set on the hyperfocal distance. Lets you snap away without worrying about focus and worry more about the decisive moment and composition. For lower light, these two films push decently well all the way up to 1600 (gets pretty grainy at this point) so I always have a couple rolls of Neopan 400 on me. Also it's cheap.
I also usually keep a roll of Delta 1600/3200 on me for night-time stuff.
For color, I love Ektar 100. Fantastic color rendition and fine grain. Portra 400 is also great, and if you can find it, even Portra 800 is quite good for its speed.