Though you do have the right to see the letter, you are more or less required to waive that right, as LNin explained. If you don't waive the right, any letter, no matter how well written, will probably be just about as good as:
"To Whom it may concern,
Sarah got an A in my Organic Chemistry class, I didn't really know her very well, but my TA says she asked some questions now and then.
-Dr. Jones"
hehe.... so in conclusion, yes, waive the right.