Postby Belton » April 16th, 2011 3:33 pm
Presuming you are also writing the rest of your letter in Japanese, I would use katakana for clarity. But you can write them however you wish. The only thing is, if you use kanji you should probably give the reading you want to use on its first use because names often lack context to give a correct reading.
Also, people use katakana, hiragana and kanji depending on how they feel. My wife's grandmother only uses hiragana for her name. (I can't remember it offhand, (because I've only ever used 祖母さん!) but it uses the old ゑ character) I have friends who, although they have kanji for their name, use katakana or hiragana in preference to kanji.