Best City for Public Transportation?

So, basically, I will be getting my degree within 6 months, and I will have a job that allows me to live in any city of the U.S., no matter how expensive the cost of living is. I am a mother of a 1 1/2 year old, and I'm looking for a city that has AMAZING public transportation (clean, safe, goes everywhere,... show more So, basically, I will be getting my degree within 6 months, and I will have a job that allows me to live in any city of the U.S., no matter how expensive the cost of living is. I am a mother of a 1 1/2 year old, and I'm looking for a city that has AMAZING public transportation (clean, safe, goes everywhere, etc.). I do not want to be dependent on a car, but I have lived in cities where waiting at a bus stop meant putting your life in danger. Ideally, I'd like to be able to take my son to school and on errands via public transportation without having to worry about our safety.

Also, do you know of any cities that are generally good places to raise a kid? I'm not looking for small town U.S.A., either- I would like to be close to good art museums, zoos, good schools, etc.

Oh, and I forgot to mention that both San Francisco and Portland are not possibilities.
Update: Oh, and Canada (ie Vancouver/Ontario)is a possibility, as well.
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