I am glad to see so many Malagasy on bicycle! Minibuses (bush taxi) are often packed with several bicycles above the many bags on the roof! This makes Mada an ideal destination (and easier than South Africa) to combine bike and minibus.
A word on road conditions: no highway with multiple lanes! The national roads are 2×1 lanes and quite decent, most of them are tarred but with some holes every now and then. This is the level of old departmental roads in France! These holes make the driving for 4 wheel vehicles quite slow, but not a big deal for 2 wheels. Secondary roads are often much more difficult, bumpy and / or just tracks, sometimes with a lot of sand. These too sandy roads are the hardest on bicycle, sometimes even not drivable: it is then necessary to have 4×4 or a good motor bike.
In Moramanga, Antsirabe, Tulear and other provincial cities, ‘pousses’ (push, bicycle rickshaw with 2 front facing seats) advantageously replace the 4L of Tana as a local taxi. Some are imported from China but many also built here (soldering the tubes, but doubt they produce the tubes). In Manajary, the manual rickshaw (guys running) dominate. Tulear, a big city, has many motor rickshaws like in India.