good plan, I am sure your girlfriend will have fun riding her own bike in SA.
first question - what is a dt350 - I think you mean a suzuki dr350.
ok. me an my girlfriend bought a bike in BsAs Argentina in 01.2002 and sold it after 23.000 km in Bogota Colombia. we bought a Honda XR200R Model 2000 in nearly new condition, the bike was made in Brazil.
you will travel north to south. ok. so maybe to buy in Equador or Colombia. I dont now much about prices in Equador as I only stayed five or six days. But I spend more than three month in Colombia. Bikes in Colombia are expensive, good for selling but not good for buying. suzuki dr350 hard to find in Colombia. many bikes from brazil 200 or 400 cc. yamaha makes the xt600 and xt225 in medellin.
to find spareparts more easy it would be good to buy a bike made in SA - and also it is more easy to sell.
one option is also to buy a bike from a traveller over the HUBB.
paperwork. we registered the honda in bsas in my name - a nightmare of paperwork, but possible. but than we had problems to leave the country with the bike and had to make fake papers for the bike ... so, Argentina is not the best place to buy. If you sell, just tell the buyer that he has to do the paperwork, for him the price must be good, so its worth the hassle - or no papers are needed - like in some parts of colombia ...
for more details email me direct
mika kuhn from vladivostok russia