[KyleGoetz]

It feels good to me: Certain parts seem very well written (and perhaps overly formal), but I'm not at a high enough level to say it's all correct. I almost want to ask if a native speaker did the translation for you, but I'm sure a native speaker would come here and call me an idiot for missing some obvious grammar mistake in the translation

One thing to note: it will hurt the eyes of someone to read a 100% hiragana letter that uses spaces, too. I found it very, very difficult to read what you have posted because of the spaces and because there's nothing but hiragana.

I'll provide a kanji version of what you've written:

日本に滞在中は大変のお世話になりました。

一緒に過ごしたときのことは決して忘れません。みなさ んから受けたおもてなしに対する感謝の気持ちは言葉で は言いつくせません。

期間は短かったのですが今では皆さんが私の家族のよう に感じています。これからもお便りを交換しましょう。 そして将来また皆さんのところにお邪魔したいと思って います。

本当にありがとうございます。

I'm thinking it should be ございました at the end, though. We'll see what better speakers than I think!