Carl's Tavern is your neighborhood "Cheers" kind of bar. It's full of a set of friendly locals, and it's a family run business that's been around for "ever" in the Monroeville area. If you go in during lunch, it's a quiet and nice atmosphere where you can chat with the bartenders (Brock and Russ are great) and feel at home. If you feel like sitting at a table, they have plenty of tables in the back of the bar and you will get service back there.
Carl's is also a great place to go at nice and have a few beers and chat with those around you. It's a very friendly set of people who go there, and there are a lot of good beers on tap.
In terms of food, the fries with cheese are a personal favorite. The fish sandwich is also very good, and very filling. If you have a big appetite, these are great choices.