I am in SA right now.
i don't know dullstrom so far, but i can give you some information about southafrica...
the streets are not so bad, but be prepared to have at least one spare tube and a good pump, or use 23mm tires because there is a lot of crap lying everywhere.
be prepared that cars, taxis(white minibusses) and trucks don't have any mercy with cyclists, so better avoid roads with much traffic.
on most roads you will find an emergency lane which gives you at least a little bit of place
ah...now i have seen where you are going to, actually i passed that region last week because i have been on site in nelspruit...anyway
nice reagon, a lot of hills/mountains, the regions is between 1000 and 2000 meters high, so if you are not use to this altitude don't wory if you speedometer shows less than you are used to.
Additional, be prepared to have days with 40+degress and 100% of humility, and during the night it might cool down to 10degrees
near that place is a big paper mill(Sappi Ngodwana), try to, if you can to avoid this area because it stinks(depending on the wind you can smell it 100kays away)...during the paper-producing they blow a lot of chemicals into the air, such as SO2 what stinks terrible( i know that, because that is the reason why we have been there)
due to the papermill there are a lot of trucks around this area delivering wood from the forests around, and others on their way to mozambique so watch out.
but anyway, you are going to enjoy that trip, the region is one of the most beautiful here in southafrice due to the large forests and mountains, people are very friendly and the food is good