I've always used volume up. I even powered down my phone and booted into recovery just to double check. Have you tried that button combination? If not, it wouldn't hurt to at least try.
i seem to remember having trouble getting to recovery when i first got my fone, my method is to press volume down then home then power and hold.. as soon as i see the lg logo i let go.
i hit those buttons in sequence, instead of trying to press them all at once, and i dont wait till the lg logo dissapears, i let go the second i see it.