Japanese street addresses are written in combination of kanji, hiragana, and katakana as they are applicable to the individual prefecture, city, town names. For an address in Ginza, Chuo-ku, Tokyo prefecture, for example, you start off with 東京都 ("Tokyo to" = Tokyo prefecture in kanji) 中央区 ("Chuo-ku" Chuo ward, all in kanji), 銀座 ("Ginza" in kanji).
But there are some city names such as Saitama city in Saitama prefecture - while the prefecture name is written in kanji like 埼玉県 ("Saitama ken, Saitama prefecture, all in kanji) the city name is *officially* written like さいたま市 ("Saitama" in hiragana, and "shi" = city, in kanji).
I don't know any city or town name that is written in katakana - as explained by the earlier poster, katakana would be for imported/foreign words. But there are apartment/office building names given in katakana, so that would be written in katakana.
There are no rules depending on who is writing it... young schoolkids not knowing many kanji yet but trying to send a letter to a friend/teacher can write in hiragana. If you are wondering how, as a non-local you might write addresses, you can write it out in "romaji," which is a romanized writing system. Is this what you were wondering about?
