Caltech is a small campus with a good amount of diversity in some respects and none in others. In one way or another, all the students at Caltech are "nerds." Everyone here likes science. Techers listen to a variety of music, ranging from classical to hard rock. They play sports (if they have time). A fair amount of the male population likes video games, and the girls get a kick out of shopping. The scientific interest of Caltech students ranges from molecular biology (cloning absurd amounts of DNA) to highly abstract math and hours upon hours writing proofs. The student personalities are very diverse considering there's such a small pool of students.
The ethnic diversity is another story. The school is populated with predominantly Caucasian students with those of Asian descent coming in at a close second. Bottom line, the school does not have many Hispanic or African American students. However, many of those minorities who do attend Caltech participate in a program called FSI (Freshman Summer Institute) the summer before starting here. FSI lets the students know what Caltech is like and helps them to adjust. Caltech does not admit students based on a quota system; rather, it admits them based on merit. Caltech is a tough school, and without a certain academic background, the students would not be able to succeed. There are a number of international students here, creating some diversity. Caltech has students from Singapore, Pakistan, Russia, and many other places. On the whole, any person who comes here will meet a wide variety of people who have different perspectives on life, different family backgrounds, different heritages, different languages, different accents, and many different interests.