Bob, Jennifer (michswiss) covered the details. If you check her work you'll see she knows what she's doing.
I've been doing street since 1953 in Korea and I've used a Kodak Pony, a Nikon D3 and just about everything in between, including a Rollei. My favorite camera in the sixties was a Leica M4, but from what I've seen and read, the Leica M8 and M9 are too undependable to consider for street work, and my darkroom is gone, so I'm not going back to film.
Jennifer mentioned she uses three primes. I normally use one: a 50mm on full frame, or its equivalent on any camera that's less than full frame. Very occasionally I'll switch to a 35mm or equivalent, or even a long zoom on my D3. It's not easy to do street with a D3 and a 28-300mm zoom, but in a tourist town during tourist season you can get away with it. Without the tourists my favorite is an Olympus Pen E-P1 with a 25mm lens, which gives me a 50mm equivalent. As soon as the new four thirds 25mm Leica Summilux gets out I'll put that on the Pen. I'd hoped Nikon would come out with a really good, small, APS-C mirrorless, but they let me down, so I'll agree with Tim and K that four thirds is the best solution at present. You'll need to try different things to see what focal length works best for you. A 50mm gives you roughly the perspective of the naked eye, but a lot of people like to work in closer and accept the distortions that go with a short focal length. It's a personal thing.
I rigged the Pen with a Leica 50mm bright line auxiliary finder. Of course you can't focus with an auxiliary finder, and trying to focus manually on a LED screen is almost hopeless, so I autofocus on something about 10 feet away, set ISO on auto, set the lens on f/8 or f/11 depending on light conditions, and use zone focus with the aux finder. Now I'm in good focus from about 7 to 14 feet and in fair focus from about 6 feet to many feet. If, as Jennifer pointed out, the time I have available is a fraction of a second, all I have to do is raise the camera, frame the picture and go click.
I'm always delighted to see someone on here interested in something besides landscape, flowers, and other kinds of photography that don't involve the real world of people, but street photography is a very, very personal thing. You need to work out your own approach. Good luck with it and I hope we can see some of your work.