Petco Park is a great ballpark with fantastic weather, mediocre hot dogs with only half-interested baseball fans. The stadium is beautiful, modern and located right in the historic Gas Lamp District of downtown San Diego. The sight lines are excellent, the Park at the Park area behind the outfield is neat, however Padres fans are a little weak in their support of the Padres. Not sure what it is but the place does get loud from time to time.
Anyway, about my seats...section 315 was where my season tickets were for a season. I couldn't go to every game so it became a hassle getting rid of the tickets which is something I should have thought of ahead of time.
There are technically two parts to this section. There's the Upper Box portion and the Upper Reserved portion. The Upper Box consisted of rows 1-4 and the Upper Reserved is made up of rows 9-29.

If you can get some upper box seats, go for them. They offer the closest view and feels like it's own private small section since it's kind of detached from the rest of section 315. With that being said, row 9 is also technically the first row in this section but there will be a lot of fans walking around in front of you if you sit there. The plexiglass in front of row 9 is also a little annoying. For the most part, you can sit wherever you want in this section as long as you have an upper level ticket. Enjoy your seats here and Go Padres!