Have you checked gurbanifiles.org? There are many different files there - the files with English translations can be found at
Files with English Translation & Phonetic Transliteration of Sri Guru Granth Sahib .
What I've found useful is to print (or in your case, download to iPod) the version that has the English translation and the transliteration from Gurmukhi into the Roman alphabet. (I don't yet read Gurmukhi, so I don't print the version that includes it.) I follow along on the printout while listening to a recording of the bani - I like Dya Singh's recordings, and there are many others available as well. The Sikhnet Gurbani archive has a wide range of recordings to choose from.
For me, listening to the words while following along on the printout has helped me begin to (just barely) understand the original text. Any four-year-old Punjabi child can understand and speak better than I can, of course, but I have at least reached the point where I can listen to the Japji and think "Oh, this is the section about 'If anyone should claim to know Your limits, he shall be known as the greatest fool of fools!'"
I think it helps that the recordings are sung (or chanted), not just spoken. There are a few passages that I've been able to memorize, and it's because I can "hear" Dya's voice in my mind, singing them. Of course, it also means I sometimes realize that I'm sitting on the bus, quietly singing to myself, "so-ee so-ee sadaa sach saahib saachaa saachee naa-ee". I figure Waheguru doesn't mind that I can't carry a tune, and I'm singing quietly enough that the other passengers can't hear me.
