Walking up to my seats felt like walking up a mountain. That feeling will probably vary from person to person. Our section was mostly empty, about half full for the game we went to so we could pretty much sit where we wanted. The seats we bought were for row 22 but we moved down to row 13 or so.
Was grateful that our seats had cup holders; not every ballpark includes them believe it or not. There is definitely a lot of diversity in Petco Park's design, but it all still blends together very well.

Petco Park is in perhaps one of the nicest and most developed areas of San Diego; the GasLamp District. So you should have no fear in walking back to your car at night. Tons of things to do in the area; check out some of the ships and the Coronado Bridge if you get the chance. There's lots of history down there.