There are generally very few formal language schools in Maputo. Those that do exist teach Portuguese, English or French. There are no formal schools that teach indigenous languages.
Although formal opportunities to learn local languages are somewhat limited in Mozambique, it is very likely that you will be able to partner up with a native speaker to trade language lessons. This is a great opportunity to learn not just the grammar, but also the customs, culture and area more broadly. Questions about gift giving, festivals, nightlife, and greetings can be addressed without worry. In the best-case scenarios, an exchange partner is not only your ambassador, but a friend. Look for a tandem partner through EasyExpat's Mozambique forums.