I have all my important documents uploaded to Google Docs but, as you say, if you've no connection, either wi-fi or 3G, it's totally useless. This is a big problem for me when I go to mainland Europe as data costs are pretty horrific.
I solved the problem very simply. As well as Google Docs I also have all my documents on my phone (Samsung Galaxy S2). It came with Polaris office and I also purchased Documents To Go and both work perfectly.
I simply plug in my phone using a USB cable, navigate to the 'Documents' folder and drag across a folder from 'My Documents' on my PC.
In my case I use a folder on my phone, as that's where I've got the most space, but you could also put them on your SD card.
I drag across large folders (one with 700 documents) that have sub-folders, which have other sub-folders, and the integrity of the folder hierarchy is never compromised. Using either Polaris or DTG I can then navigate the folders on my phone as easily as on the PC and Word documents, Excel spreadsheets and pdfs are all read without a problem.
Using this method I have access to all my documents when off-line and, by using Google Docs as well, I have the security of safeguarding them in the cloud.