If i write a letter to a japanese person, shoould i write it with latin letters or with kanji?

Hey not sure if this is the right sub for my question but ill just try.

I wanna write a fan letter to a favourite mangaka of mine, but i genuinly have no idea how to write japanese.

Im a bit scared that if i translate all the english words into kanji my handwriting wont really be readable since to someone as untraines/learned as myself its more like drawing smybols then writing text.

Perhaps any other advice?