Tom,
How about Cottman Ave & Roosevelt Blvd? Near that location? I would say center city, but personally I really don't like center city that much, Cottman is about 10 miles from there and should be close enough to Fishtown. My vet is located on Bustelton ave (Rhawnhurst Animal Hospital), Dr Dennish, maybe you can buzz them and find out where a good location would be?
I don't know much about South Philly, but I know one thing, not North Broad, lol! Or Olney! I grew up in Nicetown then we moved to Olney, then moved to the Far NE. I was thinking the greater NE, if you remember Korvette's on the Blvd, that would be pretty good location too, right near Chuck-n-Cheese.
Any other Philly folk out there wanna chime in feel free