A riddle about an Irish family is:
 
Q: Where does an Irish family go on vacation?
A: To a different bar.
 
The joke has been cited in print since at least 1997. This description of the Irish is often regarded as offensive, however.
 
   
Google Books
Jackie “The Joke Man” Martling’s Disgustingly Dirty Joke Book
By Jackie Martling
New York, NY: Simon & Schuster
1997
Pg. 292:
Where does an Irish family go on vacation?
To a different bar.
 
Google Groups: alt.humor.puns
Irish jokes - good ones please
John Zumbrum
3/23/97
Q: Where does an Irish family go on vacation?
A: To a different bar.
   
Google Groups: rec.humor
irish quickies
Merv
10/12/00
(...)
Where does an Irish family go on vacation?
A different bar.
 
Google Books
The New York City Bartender’s Joke Book
By Jimmy Pritchard
New York, NY: Warner Books, Inc.
2002
Pg. ?:
Where does an Irish family go on vacation?
A different bar
   
Twitter
Kristen‏
@JustALilBirdy
Replying to @joeymcintyre
@joeymcintyre Q: Where does an Irish family go on vacation?
A: A different bar.
11:13 PM - 21 Apr 2009
 
Twitter
Debbie Winkler Estes‏
@GiggleFlower
Where does an Irish family go on vacation? A different bar.
5:53 PM - 23 May 2009
 
Twitter
Tasha P‏
@OfficialTashaP
Where does an Irish Family go on vacation? A different pub #offensive
9:16 PM - 23 May 2010
 
Google Books
The Illustrated Dictionary of Snark:
A Snide, Sarcastic Guide to Verbal Sparring, Comebacks, Irony, Insults, and Much More
By Lawrence Dorfman
New York, NY: Skyhorse Publishing
2013
Pg. ?:
Q: Where does an Irish family go on vacation?
A: A different bar