I see. To do you so you'll need to create the content in both language by creating multiple blogs or posts/pages. Otherwise you can use the translation widget: http://onecoolsitebloggingtips.com/2011/02/14/translation-widget-for-wordpress-com-blogs/
There are no restrictions if you setup a self-hosted WordPress.org blog instead of a WordPress.com blog, but there are some added responsibilities. We have hosting recommendations at the following link if you are interested.