Thank you sddfdds. Your solution worked for me, and I'm glad you found it.
I automount a half dozen Truecrypt volumes at once on Mint 14 Cinnamon to do my work, which was always blanketing my screen with Nemo windows.
Two notes: (a) I had to install dconf-tools from the Software Manager to get dconf-editor; and (b) after drilling down the org.gnome.desktop.media-handing tree, the comment for the automount-open option refers to Nautilus. Turning it off worked just as well for Nemo.