First, congratulations on choosing a very important and rewarding career!
Here's what you need to know. There are so many (well-paid!) opportunities out there for translators / interpreters these days, but certification is essential, and it is not easy to achieve. You would think that fluency in two languages would be enough, but it is not.
You are absolutely correct in suspecting that a major in your non-English language is going to be most helpful to you in the long run.
If you do not attend one of the universities below as an undergraduate, you are going to have to pursue graduate work at one of them after you earn your BA. These are the schools that offer ATA-certified T&I (translation and interpretation) programs that will help you tremendously in preparing for ATA certification.
Most of these programs require at least 300-level (third year) courses in the non-English language of your specialization. In addition, any coursework you take in English would be fine (especially things like Business and Administrative Writing), but courses in Linguistics will be even more important.
Here is the list of colleges with approved T&! programs. You would be wise to do an internet search on each program's requirements, and even to correspond with the program directors in order to get more specific information.
I have also included the ATA website below. There is a TON of information there that you will find to be very helpful.
I wish you every success!
American University, Washington, DC
Arizona State University, Tempe, Arizona
Bellevue Community College, Translation and Interpretation Institute, Bellevue, Washington
Binghamton University, Binghamton, New York
Brigham Young University, Provo, Utah
California State University-Long Beach, Long Beach, California
Florida A&M University, Tallahassee, Florida
Florida International University, Miami, Florida
Gallaudet University, Washington, DC
George Mason University, Fairfax, Virginia
Georgetown University, Washington, DC
Georgia State University, Atlanta, Georgia
Hunter College, New York, New York
Indiana University, Bloomington, Indiana
Iowa University, Ames, Iowa
James Madison University, Harrisonburg, Virgina
Kent State University, Kent, Ohio
Marygrove College, Detroit, Michigan
Marymount-Manhattan College, New York City, New York
Miami Dade College, Miami, Florida
Montclair State University, Montclair, New Jersey
Monterey Institute of International Studies, Monterey, California
National Hispanic University, San Jose, California
New York University, New York City, New York
Ohio State, Slavic & East-European Languages & Literature, Columbus, Ohio
Pima Community College, Pima, California
Pittsburgh University, Pittsburgh, Pennsylvania
Rose-Hulman Institute of Technology, Terre Haute, Indiana
Rutgers University, New Brunswick, New Jersey
San Diego State University, San Diego, California
State University of New York-Albany, Albany, New York
Southern California School in Interpretation, Los Angeles, CA
University of Arizona, Summer Institute of Court Interpreting, Tucson, Arizona
University of Arkansas, Fayetteville, Arkansas
University of California, San Diego Extension, San Diego, California
University of Charleston, Charleston, South Carolina
University of Hawaii, Honolulu, Hawaii
University of Iowa, Iowa City, Iowa
University of Massachusetts, Amherst, Massachusetts
University of Nebraska-Kearney, Kearney, Nebraska
University of North Carolina-Charlotte, Charlotte, North Carolina
University of Texas-El Paso, El Paso, Texas
University of Texas-Dallas, Dallas, Texas
University of Washington, Seattle, WA
University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
Wake Forest University, Winston Salem, North Carolina
Answered By: Professor X - 3/1/2007