Happy St. Patrick's Day Everybody!
Here are some useful expressions that may come in helpful...Also great for useless trivia to "impress" others at the pub! sláinte mhaith!
http://www.irishgaelictranslator.com/translation/topic67327.html
Happy St. Patrick’s Day! (singular)
Lá Fhéile Pádraig Sona Duit
La ale-lah pwad-rig son-ah ditch
Happy St. Patrick’s Day! (plural)
Lá Fhéile Pádraig Sona Daoibh
La ale-lah pwad-rig son-ah jeev
A pint of Guinness, please
Pionta Guinness, le do thoil
Pine-tah Guinness, le doh hull
A pint of green beer, please
Truly, this is an abomination. Please don't. 
Give me the same as the man on the floor!
Tabhair dom an rud céanna mar atá ag an fhear ar an t-úrlar!
Toast:
sláinte mhaith
Variations of this toast exist, it can for example be expanded to sláinte mhaith "good health" in Irish (mhaith being the lenited form of maith "good").
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Here's some cool clip art for the occasion:
Guinness:
DARTH VADER And Guinness:
DARTH VADER and Guinness...Enjoy A Taste Of The Dark Side:
Replies
It looks like you'll have to highlight the phrases you want to see since the background and the print are all Guinness black. Great way to quiz each other! :o)