Maps are freely and easily available at
Google Maps Just type in Panama City, Panama, and you will see a clearly demarcated map of the city.
Please keep in mind that while walking around may seem appealing, in practice, it is not always the best way to go. Taxis are cheap, plentiful and helpful--a lot of '
taxistas' know good places to go and have some advice on the hotspots. Poke around the site, there are lots of threads that discuss the info that you are looking for; I also recommend just picking up a guidebook for when you are there and don't have instant net access. I love the Lonely Planet guidebood, but Amazon can give you comprehensive lists of the guides available.
Cheers.