I'm taking some exception here. I have two children (young adults) that live near the art museum, and I visit them often. Almost every time I'm in the city we take the bus system. It's easy to use and cheap. Ancillary benefit is that if you dress like you're homeless they let you ride for free so some around here may qualify.
But seriously, I ride the buses often and haven't had issues, but if you're concerned than take an uber or a cab, and make sure you know which cab companies are legitimate.
Philadelphia, like all cities, is a collection of neighborhoods. You should generally try to avoid the bad neighborhoods and stick to the better ones. For example, Frankford Hall is in the Fishtown neighborhood, which is just called Fishtown. Fishtown is almost fully gentrified which means it will be cleaner (relatively) and safer (much) than those neighborhoods that haven't experienced gentrification.