Hi Jim,
Yes, there is a way to delete downloaded maps. Go to your "Saved" tab and then find the map on your saved maps list that you would like to delete. Then swipe to the right across the name of the map, and a "Delete" button will pop up. Tap "Delete" and your saved map will be deleted.
Since you are planning to use our app in Southern Africa, please check out our additional user added sources if you have not already. Simply open this link in Safari on your iPhone or iPad, and tap on the sources you would like to add. Gaia GPS will automatically open and load your new map source. For Southern Africa, I would recommend adding the ESRI World Topo map source. If you are going to South Africa, I would also check out the HikeBike.de map source, especially if you are going to be traveling in cities as well.
Please let me know if that solves your issue or if you have any other questions, comments, or concerns.
Regards,
Savannah