Japanesepod101 is an excellent resource for all levels. It offers worksheets and audio downloads. It also provides cultural things in conversation to be made aware of. Many of the beginner lessons are free with intermediate and advanced lessons paid by month subscription.
Getting a phrasebook (and it can be a secondhand phrasebook, you don't have to get the latest as basic expressions don't change) would be the cheapest way - free if you can get it from friends or Freecycle or really really cheap (as in ¥108 for a book) if you can get it from recycle bookshops like Book Off. Then as soon as you get to Japan, practice using them wherever you go.
I think memrise.com could also help you learn Japanese. Their point system is interesting, and you could hear them, and you could choose the "romaji" (using alphabeth) one. I guess no need to learn all hiragana, katakana, and kanji if you only plan for a short visit.
I will support Yanni - memrise is a very good free resourse which helped me from the very beginning of learning Japanese.
Also I like www.punipunijapan.com, because the videos are bite-size but informative enough. Plus the videos are super cute.
And of course Waku Waku Japanese lessons on Youtube. I used them when I didn't know anything in Japanese.
- Kanji-Q. Free
- Human Japanese - By the far the best app ive ever spent money on. $10
Also, try doing a language exchange with someone in your area: a friend, a teacher, etc. You can go out to dinner and just do half in your language and half in theres. It's quite nice.
erin.ne.jp/en/ must be a good way to start. It is actually linked to a book version but the site can be really helpful for beginners as it offers video with native japanese people speaking, lessons and exercices.
I also recommend to learn kana (hiragana + katakana) with an app (one can learn and review what has been learn at any time of the day), then move to printed hand writing exercices of kana, which can be found on Japanese-Lesson.com .