One feature of WK is that you don’t learn from easy meaning to difficult meaning, but from visually easy to visually difficult. That also means, that you will learn some important vocabs in pretty high levels. And you should keep in mind, that WK won’t teach you “all the vocabs”. The main goal is to teach the kanji! But to really know a kanji, you should also know some words, which use this kanji.
If your goal ist to really learn Japanese, this technique is very useful! But even if you just want to catch up some words and kanji, WK is is super useful! Because of the SRS-System you will learn so much more that with other techniques!
In your case I would give WK a try! If you want to make fast progress, here is a wonderful post “How to gain 1 Level in 1 Week?”. And on the other hand I would learn some useful phrases (the usual “good day, good evening”, how to ask for directions ect.) as well as some grammar (e.g. the chapter Basic Grammar in Tae Kim’s Guide to Japanese Grammar.
Btw: do you already know katakana? They are the Japanese alphabet to write foreign words. There are TONS of english words used in Japanese. The fastest way to give you a little “Japanese boost” before a trip, is to learn them!
(just as an example: the yahoo-start-page with translations of the words written in katakana)
~T 
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