You do not need to do this when syncing with Dropbox. The information about the currently open files is stored in one of the folders in the Sublime Text 2 directory. Therefore, you can symlink those three directories and leave one of them local to the machine you are working on. Specifically, you only need to sync the "Installed Packages", "Packages" and the "Pristine Packages" directories. Do NOT sync the "Settings" directory.
You do not need to do this when syncing with Dropbox. The information about the currently open files is stored in one of the folders in the Sublime Text 2 directory. Therefore, you can symlink those three directories and leave one of them local to the machine you are working on. Specifically, you only need to sync the "Installed Packages", "Packages" and the "Pristine Packages" directories. Do NOT sync the "Settings" directory.
On windows:
mklink /d "Installed Packages" "path\to\dropbox\Installed Packages"
mklink /d "Packages" "path\to\dropbox\Packages"
mklink /d "Pristine Packages" "path\to\dropbox\Pristine Packages"
On Linux:
ln -s path/to/dropbox/Installed\ Packages Installed\ Packages
ln -s path/to/dropbox/Packages Packages
ln -s path/to/dropbox/Pristine\ Packages Pristine\ Packages