This was my go-to bar in Pittsburgh. If there was ever any question about what to do on a weekend night, we would inevitably end up at Kelly's. It has a super laid back atmosphere and they always have good music playing. Be on the lookout for when Zombo DJs, because that's the best. It does get super crowded on the weekends and during happy hour, so go early. But in the summer months it's especially nice because they have a fairly large back patio, making it easier to get a table.
The food is pretty good (Pittsburgh bites and the mini mac were my favorites) even though they got rid of the greatest item on the menu-- the tater tot poutine. They have a decent beer selection and a really good list of retro cocktails. Every night there is a different cocktail special for $4 all night and the happy hour from 5-7 let's you get appetizers for half off.