If I write a letter to someone in Japan using Romaji ...is it easy for them to understand me..or do I have to learn Hiragana before they can understand me..

Most people can read Romaji. But it is true that it is more difficult for us to read things in Romaji. Writing in hiragana, katakana, and kanji will make things more clear and help us understand more quickly. But once again, if you write a letter in Romaji, most Japanese people will be able to understand you.

nihonjin ga romaji wakarimasu ka? (Japanese people understand romaji?) Did I say that correctly? Anyways, that's the real question :P

Yes! Japanese people can read and understand _Romaji_, but would rarely be used amongst themselves. :lol:

Is Romaji the way Japanese students learn to read hiragana and katakana?

Konnichiwa! Romaji is NOT the way Japanese students learn Hiragana and Katakana. It's actually quite the opposite. Japanese children learn Hiragana and Katakana FIRST. Japanese writing system includes Hiragana, Katakana and Kanji. Romaji is not part of the Japanese writing system - Romaji (literally, "Roman letters) exists to help English speakers be able to read and write in Japanese - and it is possible to become fluent in Japanese without learning the three writing systems... BUT, if you want to go beyond books that have these romaji transcriptions, it's a MUST to learn Hiragana and Katakana. So, ROMAJI is primarily used for the convenience of foreigners! :P