Often the best resource for crime and safety issues can be the local police department or county sheriff's department. They have access to the most accurate and current information and are generally very willing to be helpful.
I live in 19146 and I can tell you that it's a fantastic area code to reside in. There is a town watch program that i am a member of. Here is the link http://www.sosotownwatch.com and in case you want to contact the local police department, it's actually the 17th district. that will respond to any questions that you may have. I hope this will help you. Here is one more link.
I agree it's best to check with the local police district for the information you require. They track the rates for most types of crime. 19146 borders Rittenhouse Square and includes Fitler Square both very high end neighborhoods so I'm sure you will find the crime rates very low. I don't know if the district is for the whole zip, but its the 9th police district.
For an accuurate answer, why not visit the local police department and ask all your questions, they'll gladly answer and you'll be happy to have heard the information firsthand. Keep in mind that real estate professionals are prohibited from enticing a buyer to buy, or not, in specific neighborhoods.