I don't know why the backslash keeps showing as text when I enter (setq paper_size "Tabloid (11x17\")")
Another way to think about it: the backslash isn't "showing" as a character, but rather, the backslash and the double-quote, combined, are one character in AutoLisp string-formatting terms. When you apply that string within something else [a Text or Mtext command as textual content, an (alert) or (prin...) or (prompt) function, etc.], the combination goes back to being just the double-quote character, because the "clue" that the backslash provides has done its job and is no longer part of the string in those applications.
Sorry for the false alrm guys. It turns out my troubleshooting skills were to blame. I was only looking at the string returned, not running that string thru the program. When I realized that I needed the backslash It all came back to me.
Thanks again for all the quick responses. As usual, this forum did not disappoint me.