How about ~/Desktop? That's mirrored in iCloud for sure. Possibly also other paths, but that's sort of hidden knowledge.
Usually when I use it I just drag files into the shortcut in Finder, but I guess that's a point for Dropbox. Of course you can just make symlink with ~/iCloud (I'm not at my Mac right now, but as I type this I have a feeling that there is some path in your home folder to iCloud or maybe I've already linked to it.)