While you are populating your site, published (i.e. not draft or private) pages and posts will be viewable to anyone who has the link. However, you can set your site to “discourage” search engines from indexing your site so that it won’t receive a large amount of traffic until it’s ready.

In the dashboard navigation menu, choose Settings > Reading and check the box next to “Discourage search engines from indexing this site.” When you are ready to “launch” your site, simply revisit the settings page and uncheck the box.