Every time I go to Las Vegas I end up at O'Sheas at some point. I'd recommend walking back to the bar that is just in front of the 'food court' as you can almost always find a seat. The drinks are cheep, and not just by Vegas standards, but they are still made with quality alcohol and taste great. The service is great and the servers are always fun without having to 'put on a show' for everyone to have a good time.
I'd highly recommend starting the night here as it is hard to have a bad time at O'Sheas.