I personally would second (or third? or fourth?) the suggestion to go with a good JSL (Japanese as a Second Language) text rather than a text meant for Japanese kids. But avoid romaji like the plague. It is useful for learning hiragana and katakana, but once you have memorized them (or basically learned them) romaji has zero usefulness, and your reading will become smoother much faster if you read in Japanese. みんなの日本語 is basically "the" Japanese textbook these days. It came out after I left high school, and wasn't used in my uni yet, so I've never used it or looked at it, but I've certainly heard of it, so it would be a pretty safe option. The advantage of textbooks over the internet is that they put a lot of thought and research into textbooks, so I think personally that they tend to be a little more systematic in their approach and they have put a lot of thought into what vocabulary to introduce when, etc. But if you are planning to self-study you should take a good look inside any textbook or reference book you choose because some are really geared to being used in a classroom setting, and may include very minimal explanation (with that gap expected to be filled by a teacher... again I haven't actually looked at Minna no Nihongo, so I can't speak for it). Using a textbook with internet supplements for things that need more explanation is also good.
The problem with texts geared towards Japanese kids is that they already know the grammar pretty much perfectly, and they have the basic vocabulary which they just need to figure out how to read. There will be absolutely no useful explanation, so it will take a while for you to even get to that level. (Which is not to be discouraging, as an adult learner you will find that you learn a lot of "big words" that an elementary student doesn't know, but still don't know a lot that they do. And that's okay because you are usually having adult conversations. You just learn in a completely different way.)
My one suggestion is music, and specifically music programs (Music Station, HeyX3, CDTV, anything with people singing). The great thing about music shows in Japan is that they always have the lyrics on the screen. This is excellent reading practice (and helps you at karaoke). Music is good because you can learn the words with the music (even if you have no idea what they mean) and follow along on the screen. Songs also tend to have a relatively finite vocabulary, so you see the same words over and over again. If there is a song you really like, go through and look up what all of the words mean. Or when you start to recognize words that occur frequently make sure you look them up. Constant exposure, through multiple inputs (sight and sound) with a little added effort on the side does wonders.
And finally, if you haven't already, look into local volunteer groups that give Japanese lessons. I don't know about Kyushu, but in my area there are several groups that offer one on one lessons for about 200-300 yen a class. The quality of the teachers can vary as most are not professionals, but if you get lucky it can be really helpful to have someone who can explain things to you. Making Japanese friends is great, but unless you have some sort of language exchange or something, you probably won't want to spend your time together talking about Japanese grammar...
There may be something good on this website...
http://u-biq.org/nihongo_fukuoka.html
