Arsenal Lanes is the go-to bowling alley in Pittsburgh. It's not perfect bowling conditions on a busy night, but if you're looking to get the most bang for your bowling buck, you should come here.
Their specials (both bowling and drinking) can't be beat. Make sure to check their website before you go. I think it's cash only (at least for bowling) so make sure to bring some along. They have an ATM on site too.
The last time I was here we came on a Friday for all you can bowl from 9PM - 12AM. We got there around 8:15 and hung out at the bar, where the bartender told us he would let us know when to line up for the open bowling. This was a huge help because around 8:30 he told us they were ready and we ran to the front of the line to secure 3 lanes (for a group of 18 people!). I'm not sure if you can reserve lanes ahead of time, but if you have a bigger group definitely get there early.
My only complaint, similar to other reviewers, is that the bar service is really slow, and sometimes there are problems with the lanes. Still, it's 100% worth it for a great night out.