Check with your PH (guide) and see what he thinks. Also be good to check out some forums dealing specifically with such firearm/hunting needs for Africa. That said, the .375 Ruger is an outstanding cartridge but as said, if by some chance you get seperated from your ammo, you're less liekly to find this new cartridge where as the more tradtional cartridges would - I think - be quite available there.
Check here:
http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/ubb/postlist/Board/20/page/1