If it's page 5 then there's a little trick, insert +5 that will tell indesign to start from the 5th page, no matter what the folio number is.
I don't think that's going to help with Print Booklet. As I read this, the OP wants to impose the entire file, but print only the third and onward imposed spreads to save a sheet of paper.
As far as I know, Print Booklet just isn't sophisitcated enough to do this. Normally you would select the page range to print in the print dialog, which you access from Print Booklet by clicking the Print Settings button (this is where you set page size and orientation), but the page range is not accessible from Print Booklet. I think the only options are to either reprint the whole bookleet, or print to PDF and use Acrobat or Reader to print the selected spreads.
Yea it seems a bit tight trying to save one bit of paper, but its really expensive! Must edit more carefully!
Making the PDF from Print Booklet gives yo more flexibility with how you can print.
Windows or Mac? Which version? Do you have Acrobat Pro?
And if you're the kind of user who likes to inspect their booklet impositions in InDesign before committing to paper, avoiding Print Booklet and using an InDesign extension like IDImposer might fit your needs better. For now, it's free to nonprofit organizations. http://idimposer.com
Requires InDesign CS5, 5.5, or 6.
Stephen Carlsen, creator of IDImposer