I usually install the xfce4 package, but the above probably works (I know it does in Ubuntu, but I've never actually tried in mint)-my Lisa vbox install is really slow b/c I don't have hardware virtualization capacity, so I can't actually get to synaptic atm. Linux Mint also has an lmde xfce version which you can download, although it is not quite as stable as the main edition and it's based on debian so it's not as new-user friendly. There is also a Linux Mint 9 XFCE version which will be supported for a while, until April of 2013 (I think).
Dell XPS 15 l502x - Debian Testing 64-bit NetInst Xfce, SolydX 64-bit Debian Testing, SolydK 64-bit SolydXK Testing
Old Gateway Pentium 4 Desktop - Arch Linux 64-bit Xfce and SolydX 32-bit Sid