I guess I was spoiled, with Spiritus my research was pretty straight forward. I had to read up on the American Civil War and Voodoo. Luckily, there is hundred of thousands of articles, photos, and books on these subjects. But Irish Travellers? Next to nothing.
I did learn that it is spelled Traveller and not Traveler. That they are distrustful of outsiders and that about half are Settled Irish Travellers.
Something else I have been able to learn is that Irish Travellers came to the UK and American in the 1850's after the potato famine in Ireland and then again after World War II. Thanks in part to the secrecy surrounding the group, there are no official population count for the Irish Travellers living in America and they are not listed as an ethic group on the U.S. census. Wikipedia suggests that their population is somewhere between 10,000 and 40,000.
I also learned that Irish Travellers speak English, but often use what is referred to as the Irish Traveller Cant (Yep, I have to work that in to the story somehow) which is a combination of English and Shelta. There are a few things that mention their strict rules of cleanliness and mention a Travellers Code, but nothing very detailed. Not a lot, but at least it's something.
Then, of course, there is My Big Fat Gypsy Wedding and My Big Fat American Gypsy Wedding. What did I learn? Their weddings and first communions are AWESOME! But I didn't really learn that much about their culture other than how hated they are by outsiders.
That brings me to what was easy to discover: People HATE Irish Travellers.
Now, you want to learn something about human nature? Read the comments attached to articles about Dale Farm. I was a little shocked by the slant of the articles. It was one extreme or another until you got to the comments where people talked about not wishing "them" on anyone, seizing vehicles on those leaving, and so on. If you look up "Irish Traveller" on the internet, you will no doubt come across articles with titles like Irish Traveller Scams from places like eHow. To make matters worse, there was the "outing" of Madelyne Gorman Toogood. She was caught on tape thrashing her daughter. Her arrest drew attention to this secretive culture.
So, what have I really learned about the Irish Traveller culture? Not a lot, but I do think that where you have a reclusive group of people it is the trouble makers that get noticed and unfortunately become the face of their entire ethnic group. But, reading the hate filled comments about them, I can understand why they remain so secretive.