The National Couples Survey asked 593 people if they've slept with someone else since being married. Here are the percentages answering yes by race/ethnicity:
* p < .05, two-tail test, compared with whites.
Samples sizes for minority groups are small--only blacks have significantly higher rates. (I know that someone having multiple partners in an open marriage would be included with the cheaters, but this type of arrangement is rare, I think.)