No. There are no limitations for languages on the sites we build. Both regular content and the administration pages can be built for Spanish and many other languages, including right-to-left page, text and site rendering.
The rule of thumb that you should generally go by is this. (Which was actually taken from another Website, but summed up everything really well): If you have the technical know-how to construct an email with an attachment, create a formatted document with Microsoft Word, and navigate through a web site, you have the skills needed for content management. It really is that easy, provided you have the right content management software.