I know of a few expat organizations in Launda.
The first is the American Women's Association of Angola. The web site is: awaangola.org/index.html This is a group of American women that have monthly meetings. Through this group there are lots of smaller groups that go to local orphanages, volunteer for a variety of activites, etc. Their website also offers wonderful information about getting around Launda, things to do, etc.
There is also the Luanda British Women's Group. This is a link to their blog: lbwangola.blogspot.com/p/luanda-british-women.html which also had an email address worth trying: lbwangola[at]gmail.com
There is also TICA, The International Community of Angola, which is also a great organization. You can contact them at tica.angola[at]gmail.com
Then, The Angola Field Group. This is another wonderful group that offers very informative wonderful speakers. Their website is: angolafieldgroup.com/ You can also email them at Angolafieldgroup[at]gmail.com
If you are interested in "running" or entertainment there is the Luanda Hash Hound Harriers as well: lh3[at]yahoogroups.com
As far as Portuguese classes, I hear the Alliance Francais is great. I am actually going this week to look into more information. If you are interested, I can reply back with whatever I discover.
Going out: the Ilha is the best place to go out, as well as meeting.seeing expats. Some popular places are Chill Out, Miami, and Don Q. Don Q is actually located in town and more locals.
I should also note that from my experience, most of the expat clubs (AWAA and LBW obviously) are majority women. However, at their functions it is both women and men. Often couples of members. I would just email the contact and get whatever information you can! The Angola Field Group has their meetings Thursday evenings which is helpful for people who work here.
I hope this was helpful! Best wished to everyone :-)