The risk of mortality from Plasmodium falciparum is non-trivial. Unless he has an allergy to doxy like I have, the risk of bad side effects is less than the risk of a potentially fatal protozoan infection, that even if he survives, will probably be with him the rest of his life. Last I checked, somewhere between 500,000 and 1,000,000 people in sub-Saharan Africa die from this strain of malaria every year. That's generally 5-10X the rate of AIDS deaths in the same area.
In any case, he will have to go to a doc to get a scrip, whether for doxy or mefloquine.
If the question were "I'm hunting the eastern cape in August, should I take an anti-malarial?", the answer would be "no."