Sure, there is. When you start the back up, I am assuming that you are doing the Main Movie only, and going straight from DVD to Conversion - a 2 pass operation. If not, the same principles will apply, anyways.
On the screen you see when you've selected Mobile and the particular conversion you want, and the disc contents have been read by Fab, look for a heading that says Substreams. Right under it will be 3 or 4 items, with a language beside each.
De-select all of these.
You have just eliminated subtitles from your copy and converted file.