Adding multiple languages is a common and effective business practice. Lots of websites do this to make sure they cover the Majority of the crowd who dont speak English Language. In US a recent census says 15% of the people are Hispanics that is almost 50 million people.
It is not possible to ignore those people when it comes to doing busines. Most of the Hispanics dont speak good English and this shows the importance to have a website in both spanish in English.

Same way in European union not all countries speak English targeting the regional language is a very important factor to reach the local business. Having a website in various languages are becoming mandatory these days so how does the search engines treat when they see the same information in different languages. From our experience search engines see only the contents and different language contents are unique to themselves.