Make sure to omit quotation marks when you search. On some search engines that limits you to the exact phrase enclosed in quotes.
Also, I did a search on "bush speech", with "match all words" and "order by post time" selected and got the transcript of his UN speech (about a third of the way down the page).
A text of President Bush's speech to the United Nations
AFAIK, the search engine here only looks at article titles, not the text of the article. So, if Cheney made some comment on Iraq and it's buried inside a WashPost article, it might be hard to dig it up.
I pinged Jim Robinson to let him know that there seems to be some use for an article body search capability. Maybe he will have some other information that can help you out.