I've seen a few Squarespace users in the forums asking why their "subdomain.squarespace.com" site is indexing on Google, and I even received a comment post on my site asking the same thing.
You can tell your searchbots where to go, by using a Robots.txt and Sitemap.xml files. I posted this earlier [here].
On almost every site I build, my first step is to keep the searchbots out of the site. Most sites are re-designs, and primarily, I would like to keep the client's visitors from finding a site packed with dummy text (before the client adds their final content) and/or view the development in progress.
To do this, simply log-into your Squarespace site and go to Website Management - Website Settings - Search/Indexing. Under "Search Engine Perameters" deselect "Allow External Search Engines to Index Site" and "Allow External Search Engines to Archive Site".
Just be sure that when you're ready to launch the site —to check those boxes!