Technically, U city is up to 50th street.
There are certain steps one must take in order to ensure safety. I've lived some major 'hoods in Philly and have been generally safe. I had one run in on 10th and Lombard when that was the hood (anyone remember the projects on Bainbridge?) But because I look over my shoulder I ended up ok. It's all in your awareness and listening to your instinct.