Sorry, but Pittsburgh (like many large cities) does not have campgrounds that are convenient to the city. You're looking at a 30 or more mile trip each way from anyplace you camp at. No matter which direction you camp at from the city, expect to spend a minimum of 45 minutes to reach the "Burgh"- and that time can be longer depending on traffic conditions. PNC Park is on the north side of the city so, naturally, you might want to camp somewhere north of the city for a simpler access to the ball park.
Because it's mountainous here and we have three major rivers, there are many bridges and tunnels that can restrict your routing. For example: you may have to drive miles out of your way to a bridge so you can cross a river, then drive miles back the way you came (but on the other side) in order to reach your destination. But, this is Pittsburgh. We understand and accept it as our way of life. However, these inconveniences can be frustrating to the point of madness for some visitors. The road system follows the terrain so don't be alarmed if you're driving on east something road and the compass in your car/GPS says you're heading south. And, there's an old saying in Pittsburgh- "The shortest route between two places is usually under construction.". Your best defense here: Obtain a good street map and use a GPS. It's easy to become disoriented here when you're unfamiliar with the area. I strongly recommend having one or both items with you in your vehicle before you attempt navigating Pittsburgh's street system.
I don't mean to scare you with what I wrote above. But, I'd rather "put the cards on the table" and educate you a little so you understand and are not surprised. Honestly, besides PNC Park, there is lots to do here. In fact, more than you'll have time for. Pittsburgh is probably one of the best kept secrets of places to visit in the US. If you have any attractions you're interested in visiting or looking for suggestions, post again and I or some other "Pittsburgher" will surely come to your aid.
Places to Camp:
PA Campground Owners Association (PCOA). Campgrounds in all of PA, http://pacamping.com/
Bear Run Campground, Portersville (Near Moraine State Park), http://bearruncampground.com/
Indian Brave Campground, Harmony, http://indianbravecampground.net/
Raccoon Creek State Park, Hookstown, http://www.dcnr.state.pa.us/statepar...reek/index.htm
Madison/Pittsburgh KOA, Ruffs Dale, http://www.pittsburghkoa.com/?doing_...86901855468750
Washington/Pittsburgh SW KOA, Washington (PA), http://koa.com/campgrounds/washington-pittsburgh/
Keystone State Park, Derry, http://www.dcnr.state.pa.us/statepar...tone/index.htm