Mint13 xfce has issues if one want to share its computer with others. This issues should be corrected in future releases and fixes should be applied to mint 13 since it's a LTS. Here they are:
1) no application is installed by default to add/remove users
2) even if I manually add the link for gdmflexiserver (to mdmflexiserver), the "new login" button in screenlock will not work in all cases. If every users has already opened a session on the computer, the locked user will have to unlock first. Said otherwise, the "switch user" is not correctly implemented (as it is on cinnamon).