How would you specifically determine whether community policing efforts are working?
This is really very hard to accurately determine. The most likely way to determine whether these efforts are working would be to look at crime rates. You would need to look at the crime rates in the area where the community policing program is in effect. You would need to compare the rates before and after the program came into effect. I think that you would also need to look at crime rates for the country as a whole or at least at cities that are similar to "your" city. If your city's crime rate drops, but so do those of other cities, then it is harder to claim that the community policing is the cause of the decline.
If you had the money and the time, you could do interviews. You would need to look at perceptions of the police in the community. This is supposed to be a big plus about community policing -- that it will make people in the community see the police more positively. But this would be very difficult to do.