First, a minor note: we RARELY e-mail anybody unless we offer the intended recipient the chance for "personal" e-mail.
Okay, concerning your name: do you want the "translation" of your name in Japanese or do you want the katakana of your name? Besides, the Japanese would use your patronym with the honorific "san" (in your case, it would be Diaz-san.) It is true of ALL "foreign" names, if not ALL names, period. The only time that is not done is when addressing an "instructor", then the honorific "sensei" is used, but ONLY in a learning situation where s/he is the instructor.
I hope I've cleared up a bit of Japanese for any/all interested bystanders (including the inquiror.)