ok
I wouldn't chose to live in DC -I have a few friends who do (but not with children).To be honset for that reason I have no idea what preschool provision is like - the schools have a bad reputation. Having said that there are definately walking communities etc. If you think DC might be an option I can ask about, check with my two friends who live there what they think (they are both american but one is married to a brit so shoul dbe able to give some insight.
We live in Maryland - Gaithersburg, basically the last stop on the metro (shady grove) - plenty of people commute from here to dc to work (including my neighbours on both sides,one by car,one by train) I think it is a 40 to 50 minute journey to the heart of dc - including 10 or so mins from our community to the metro. We picked this particular area really for the car thing. Our area is called the Kentlands and Lakelands and is a walking community. The houses are quite closely packed in (a good thing by american standards I think - unless you fancy a McMansion), there are pavements,schools,playgrounds, and a shopping area that has supermarkets, small shops, cinema etc.etc. The community was started about 10 years ago and has become quite a model for the area (Fallsgrove, King Farm are similar though not as successful imho). It is not a cheap place to live (propertywise)- but the pavements and the ability to walk sold me on the place and I found it hard to contemplate other areas when we were looking - it felt more English and less scary. The only thing I don't like about it is that it is a bit 'perfect' rather manicured, and very middle class - not much of a cross section of society - but in many ways a wonderfully safe and community minded place to bring up children.
Arlington in Virginia is a place that many young families also live, a bit more cosmopolitan and not quite so expensive - also good for a commute into dc.
Bethesda is great - but very expensive to live in I believe.
I can certainly find out more about both those areas from friends if you want me to.
I wouldn't worry too much about nursery - its more expensive than the Uk - but these areas tend to have quite a fluid population as professionals move etc. In this area at least you would probably be able to get a place in a preschool you were happy with - even it it wasn't your first choice in an ideal world
Thats more than enough for now i'm sure - happy for you to cat me - i am paid up! And am happy to help more/in any way i can.