Yes you can still do a colon cleanse if you have IBS.
My dad has IBS and he does a weekly colon cleanse and it helps him feel much better and helps keep his colon clean and eases the symptoms of the IBS.
Cleansing your colon is always a good thing whether you have IBS or not because having a cleansed or clean colon can help prevent colon cancer.
So if you want to irrigate or cleanse your colon you can and should do so because you'll likely feel much better.
Getting a Colonic or doing a colon cleanse can help ease the abdominal pain, constipation, and diarrhea associated with IBS or irritable bowel syndrome.