Enjoy the spirit of the day, responsibly of course. It'll be amateur hour out there at most places unfortunately, but there should be some good beer flowing at the usual great beer stops like Max's, Mahaffey's (owner Wayne is a classic) and Frisco Grille.
I'm not a huge fan of the Irish beers (Guinness, Smithwick's, Harp, etc.) but they should be on tap almost anywhere today. I will say Baltimore quietly has a ton of Irish bars and establishments, you can basically throw a dart at a list full of names and probably be quite satisfied wherever you land.
Let us know where you went if you went out.