Algeria suffers of not really having one common language possessed by everyone!

The official language of Algeria is Arabic but Kabyle was recently added as official as well, after much pressure from the Kabyles to be recognized.                

It is expected of foreign businessmen to speak French (or Arabic). English speaking Algerians exists but are not growing on the trees, but it is possible to find qualified translators. (CONNIMPEX can help you find one)

Well-educated people and people above forty tend to want to use French in business life; some even use it in their homes.

Working class people and people under 30 (included many educated) mostly use Arabic since they didn't study much French during the 90:s.
The further south you get the more Arabic. In the capitial Algers, French is wider used since so many people groups mix there.
The Kabyle people in the mountains prefer to speak Kabyle or French, but they study Arabic at school.  

Other people groups like the Shawis and Mzabs and Tourag would speak a local language in their homes but use Arabic (or sometimes French) at work.   

Business documents, emails and faxes are usually written in French. Official documents are supposed to be in Arabic, but it is not always necessary.

Source: CONNIMPEX, 2008