Indesign CS5 Duplex printing Postscript file

Question

I am designing a book half english half spanish—It is an instruction manual so you read the english then flip it and read the spanish.
In my Indesign CS5 document pages 1-30 are English then 30-1 again are spanish (upside down). I need to export them as a postscript file so that I can print it double sided correctly for a mock up.
I am making multiples of these books and only some are exporting to a postscript correctly and I cannot figure out why.
When exported to postscript correctly, it should look as if the left page is the cover in english and directly to the right of it is spanish but upside down, and then it alternates all the way to the end. So for example:
Spread 1: English on left right side up, Spanish on right upside down.
Spread 2: Spanish on left, English on right
Spread 3: English on left, Spanish on right.. and so on
But, some, are exporting so it shows a cover, then a blank page, and all the pages are jumbled up. (I do have "do not include blank pages ticked when exporting to postscript)
The only guess I have is that it has to do with the page and section numbering? I don't know if this effects how the postscript converts or not. But, I have several books exporting very differently to post script. Please let me know if anyone can help me figure this out!

Answer 1

I had a brief PM conversation with Stephen this morning, and it just hit me that I may have been thinking about this incorrectly. There are actually two approaches to this kind of document.
The approach I've been envisioning presents the reader with all the text on only the right-hand pages -- the lefts are all the other language upside down. But thinking back to my youth and buying some two-title sci-fi paperbacks, I think those were built so that if you tore apart the binding in the center of the book you'd wind up with two "normal" books without back covers, and there would be no page overlap between the two titles.
I'm guessing that the OP actually means to do the second, and I apologize for being dense yesterday. Seems like it was happening all week. If that's true (I mean the binding layout, not my being dense), then I understand what you were saying about Print Booklet, and there's actually a pretty easy way to make this work, I think without a plugin (though IDImposer might turn out to be even easier).
Here's the approach I would use to make a single book that can be cut apart to make two independent volumes:
First, download Scott Zanelli's Multipage Importer script from InDesignSecrets » Blog Archive » Zanelli Releases MultiPageImporter for Importing both PDF and INDD Files The script allows you to automate placing multiple pages from either a PDF or another .indd file into a new .indd doc, and it allows you to select the page range to import, the page on which to start placing, and allows scaling, rotation and alignment adjustments.
Since you have two 30-page sections, make a new 60-page file. The first time you run the script, place the first 30 pages normally, starting on page 1. Now run the script again, choosing the range 31-60, but do the following: check the Reverse Page Order box, Start Placing on Doument Page 31, and Rotate 180:
You can run this new file trough Print booklet.
The original content in the new file cannot be edited directly other than moving pages around or cropping/sizing/repostioning the page images. If you need to make text changes or other edits, do them ithe original, then update the links.