as can be expected, you've already gotten plenty of great advice from folks here. i would add two things, i think.
one is to shop around. i haven't experienced a hard sell from shops around pittsburgh so the experience should be (and is supposed to be) pleasant. places i return to include: thick bikes, iron city bikes, biketek, dirty harry's, trek of pittsburgh, and others; i'm just scraping the top of it. i suspect you'll have a good experience just about anywhere. go in, tell them the kind of riding you expect to be done, tell them you don't want to spend a ton of money because you don't know how well the bike will be used, and go for a few rides. everyone will treat you well, because if they don't, there are a dozen other places you can go. this isn't like car shopping.
the other bit of advice is to get a bike pittsburgh membership. and this isn't just a shameless plug (though it is a plug, and i don't feel any shame)! just have a look at the
membership discounts, and notice that it's worth it. i mean, if you find a bike at biketek that you like, you can pay for your membership and then some.
and thirdly (i know, i said two, whatever): come back and ask questions when you have them, or search the message board to see what others have asked. it's a great resource, and people are all only too happy to help.