I am also going to Japan for the first time in September. I do not feel anyway ready to speak Japanese. If you are just starting out and have access to a public library look for materials to help with speaking/listening such as Pimsluer CDs and a program called Mango languages for example. These will get you up to a speed on survival phrases. People seem to like Japanesepod but there was too much English for me.
While you are online, look for a textbook called Genki to learn grammar points. You should be able to get through it (not master it) by September.
Definitely stay in the WK boat as it appears to be the best way I have found to learn kanji and some vocabulary.
Also check out this thread. It looks overwhelming but just organizes a lot of the resources that you can use.