That is a lot of ground to cover!
I suspect that many neighborhoods have improved, while others have worsened.There are several sites which you should find helpful in your research. Recent information is available at http://www.cityofboston.gov/police/divisions/crimestats.asp. This will give you serious crime statistics for the last 5 years.
If you have particular concerns about a certain neighborhood in Boston or are a "crime junkie" and just want to see what the police are up against, go to bpdnews.com, you'll get a daily dose of crime stats as they arrive throughout the city and you can actually read through all the incident write ups.
A third good source is the local paper for the neighborhood in question. Here in Charlestown, the Patriot Bridge publishes a log every Wednesday with all calls that come in and what the resolution was, so you can go on Google maps or the like, and start to see where incidents are occuring.
It's likely that the BPD has spent a great deal of time and effort to summarize such trends. You should call their media relations line at 617-343-4520 and see what they can offer.
Good luck and stay safe!