I have Documents to Go on my Droid but when I open a word document (doc) it give me the choice of documents to go or quick office.
The when I go look at application info I can see that quick office is in ROM (e.g. not able to uninstall).
So you might be able to use quick office without downloading anything.
And to open a document I use Astro to navigate to the file and the touch and the document opens.