Hi Raady,
I would endorse almost everything that MadManascar (#3) says with one major exception (Hi MadManascar – glad you enjoyed your trip!). I really can’t agree with him when he says “January to March should be avoided at all costs.” I’ve been going to and travelling within Madagascar in February and March for years now, and my ticket’s already booked for February next year. It is a great time to go! (Not the least reason is because there are hardly any tourists around as they’ve all been put off by guidebooks saying “go some other time”!)
Don’t take this as a negative commentary on posting #3, it isn’t. There are certainly some things you can’t do at that time, and others that need more effort. For example, the Tsinghy de Bemaraha National Park is normally inaccessible and river trips may be more difficult to arrange. Montagne d’Ambre or parts of it and Ankarana may also be inaccessible – you’d need to check before going.
For the Malagasy taxi brousse drivers, “impassable” is a relative term. Even on notoriously bad stretches like the track from Toamasina/Tamatave to Maroantsetra north of Soanierana-Ivongo or from Vohemar across to Ambilobe in the north, transport can and does get through between January and March – less frequently than in drier months, and taking longer, but it gets through. Incidentally, it’s less the mud that’s the problem than high water levels in rivers that have to be crossed by ferries because the bridges are out. Once the water level drops, the ferries start up again.
Tropical cyclones are dangerous and destructive, and if you’re considering going to the North-East or (to a lesser extent) to the North-West, you need to check out whether anything is brewing over the Indian Ocean before you head out. You can do that by accessing the website of the monitoring station on La Réunion from an internet café: [http://severe.worldweather.wmo.int/tc/swi/index.html]. This will tell you if anything is heading in to Madagascar, what it’s trajectory will probably be and when it’s likely to arrive. As you’re wanting to go diving, then consulting this is a must whatever dive sites you’re headed to.
As far as the weather is concerned, the fact that it’s the rainy season doesn’t mean that it rains all the time. There is a lot of glorious dry weather, although it can certainly be interspersed with days of intense rain, or you can have rainy and sunny days simply alternating.
Taxi brousse travelling is just as #3 describes it, but whether you find it frustrating and likely to drive you insane is really a matter of personal attitude. I find it generally (and possibly perversely) enjoyable with all its discomforts, and you certainly have contact with local people. The time you have to wait for the vehicle to fill up can usually be passed enjoyably walking around, buying things to eat, sitting in cafés etc. You can’t do anything to speed things up (unless you want to buy all the empty seats), so chill out. They won't leave without you - they'll come looking when they're ready to go, and as a foreigner, you're easy to find. As #3 says, time has no meaning in that situation.
Must sees? Well again follow #3’s advice and look at the Bradt Guide, but if you twist my arm I’d mention Masoala National Park (especially the marine parks south of Antalaha if you’re into diving) and Nosy Mangabe in the North-East (but do check out the La Réunion website before you head out there) and Andohahela in the South-East are gems.
Anyway, if you keep all this in mind, there’s no reason why you shouldn’t have a great time visiting in January.