This may not apply to your printer, but I had the same problem with my Dell Photo 966 printer.
This is how to do it for the Dell Photo 966 printer - hopefully yours is similar! Follow the tech support instructions to get to the advanced options window, and then select the "2-sided printing" option. The "print instruction page to assist in reloading" option should then be available to deselect (i.e. not greyed out). To leave the printer in 2-sided mode by default, close the printing preferences window. To leave in 1-sided mode by default, deselect the "2-sided printing" option before closing the printing preferences window.
Choosing these options while actually printing only applies them to the document you are printing, so you need to do it from the Control Panel as described.
I am having the same problem with my 1720 printer. I am curious if there is another version of the printer driver available which has the option to disable the printing instructions. I'm also curious what dell printer support has to say, since this printer (and this thread) is at least six months old.
I found another thread here which give a similar (unavailable) solution.
I found a solution for my dell 1710.
I uninstalled the printer and then reinstalled it (with the windows: add printer possibilty). So I can choose a driver manually. On the drivers and utilities CD from Dell Laser Printer 1710 I chose the folder Drivers\Print\Win_2kXP\DKAAY2DA.INF. With the installation of this driver it works fine. There's a remark on the screen to turn the pages, but no additional instruction sheet. I guess it's just an older driver version.
If this fix still works, is there a download link to get this driver? I have an end user that used to get the onscreen prompts but not gets the printed instructions everytime.