Big City RVing

You don't indicate the size of your RV - if it's a B or a small C it will be easier to get around. We have driven our small (25 ft) C in Las Vegas with no problem and camped there. However, for most of your other cities I would rent a car or use your tow or public transport. We don't drive our car to Chicago if we go to Chicago we take the train in and stay in a hotel - there is lots of public transportation to get around and see the sights. Most of the large cities SF, Chicago, etc have good public transporation.
I guess I was never able to find enough things that interested me to want to stay 6 months in one particular large city. :)