US work visa - background check?

I am Australian. My company is relocating me to the US under an L-1 employment visa. Part of the application process requires disclosure as to any prior criminal misdemeanors. In 2000 when i was 18, i was convicted of DUI, in 2002 i was convicted again. I have indicated as such on my application, but people have since advised that i shouldn't have. My attorney located in the US has indicated i must disclose the DUIs. My question is, if you were to say 'no' i haven't been convicted of anything, how would the US find out? I can't even get that information myself without undergoing a lengthy process.