Our downtown (called Center City, where I live and have my office) is Manhattanesque in it's walkability.
There are small towns in the suburbs like Narberth for example that you can walk to the train and the downtown area and get most of what you need.
If I can be of ay more help, please let me know.
To walk to California downtown, the west-south corner of Old palo alto area probably is the best choice. Old palo alto is one of the best area in PA. To walk to big downtown -- university avenue, you can look for north side of Professorville which is also one of the best neighborhood. It has some really good listings right now.
Welcome to PA! Of course the best way is to find an experienced realtor to help you out.
We assume you mean Center City. In Philly downtown refers to South Philadelphia.
The neighborhoods of most interest will probably be Society Hill, Bella Vista, Rittenhouse Square, Head House Square and the Graduate Hospital area. Find a realtor who is knowledgeable about the Center City areas and you will be fine. Good Luck with your move.