Welcome to MobileRead, Saleem.
With multi-language books like you're describing, you'll pretty much have to go with font-embedded PDF files. You can find the details on formatting
here, including a discussion of how to format PDFs for best viewing on the Reader.
The only thing I'd warn you of is that font-embedded PDFs are sometimes rather slow about page turning on the Reader, just so you know to expect it. You'll have to decide for yourself if it's acceptable to you or not.
The other suggestion I can offer is to try font embedding with BookDesigner, the drawback there, in addition to about a 2 second page turn for embedded fonts, is that creating the books would be pretty labor intensive, since you'd have to go through and mark the non-English passages in the appropriate font, which is kinda labor intensive.
