Instead of U and S bahn, you can choose to use over-ground transportations: there are many buses and trams that travels efficently all around the city and the neighbourhoods.
MAP OF SUBWAY OF MUNICH: Click Here
Use the public transport, it is the fastest and easiest way to get around. Check for day-tickets or week tickets. See plan at http://www.mvv-muenchen.de/mvv_plaene/images/sbahn/sbahn.html
The best way is on the underground but there are lots of trams and taxi's and you can even hire a bike for those of you with more energy.