You can extract (demux) the subtitles as separate streams in IFO mode, however the .sub files are not 'VOBsub' files (there is no .idx file)files and I haven't seen anything that can utilize them.
I think there is a way to extract the subs from the DVD so that when you make them into a avi using Pocket Divx Encoder it will burn into the video.
It's easy enough to demux the subs (not using DVD Decrypter), but they are in a digital format and have to be OCR'ed to get to a text format. It's often easier to download the subs from the likes of: http://divxsubtitles.net/page_subtitleinformation.php?ID=61385
