Amherst may be the most economically and ethnically diverse top tier LAC in the country, rivaled only by Vassar. Bowdoin is a great school, and very inclusive, but it is not known for diversity.
Here’s a NY Times article about how Amherst changed itself from the all-prep school college it used to be years ago.
http://www.nytimes.com/2011/05/25/business/economy/25leonhardt.html?pagewanted=all