Ditto to everything MotoddRob said about the choice of bike.
Back in the '70s, I rode a Z1A across the Nullabor Highway there and back to Sydney, Melbourne 600km of really bad dirt each way out in the middle bit back then (the frame broke shortly after getting back to Perth).
Then in 79, I decided to ride South America, Adventure bikes had not been invented yet so I built my own. Took my daily rider a 74 3C, slightly longer rear shocks, extra-base gaskets (to lower compression) so it would run on shit gas, it did, a pair of 70's style Superbike handlebars and some small crash bars, home-made panniers, and rack for 10 liter Jerry can. there it was my adventure bike, I loctited everything I thought might need it and then some extra, a few spares including the Bosch black box (never needed it). Venezuela to Southern Chile push-started the beast in every country even on dirt roads, alone, couldn't do it now. Thousands of Km's of dirt and bad roads. A few years later myself on the same bike with Motodd Rob on his SF we did Mexico very little dirt to speak of but some horrendous miles of cobblestone highways. Take a bike you know that you can fix on the side of the road, and you can pick it up by yourself.
By the way if you think my choice of taking a 3c was odd I met 2 French Canadians in Cuzco who had lived in Melbourne and were riding Victorian (Australia) registered bikes, Suzuki triples watercooled 750's with LaParisienne full fairings. No kidding ! Proving you can ride pretty much anything anywhere.