What were the literacy rates in the Southern Colonies?

There were no statistical methods for determining literacy rates in the Colonial era, and as such, it is extremely difficult to measure. Historians gather information from a small number of historical library sources, diaries, wills, and other legal documents.
The best evidence of literacy historians use is the ability to sign one's name to deeds, parish registers, and baptismal records. Those who could not write their name signed documents with a mark or a cross. While those who signed with a mark are deemed illiterate, the degree of literacy of those who could sign their names is ambiguous; literacy consists of reading and writing competency, and the ability to sign one's name barely constitutes the latter. Moreover, reading and writing were taught separately, so an individual's inability to sign their name did not necessarily mean they could not read.
University of Montana scholar Kenneth Lockridge’s 1974 book, Literacy in Colonial New England, surveys evidence from legal records and offers tentative conclusions. He makes the case that, among white New England men, about 60 percent of the population was literate between 1650 and 1670, a figure that rose to 85 percent between 1758 and 1762, and to 90 percent between 1787 and 1795. Note that the Puritans of New England placed a great emphasis on literacy. Rates were comparably lesser in the Southern Colonies, particularly in rural areas. There were no public school systems in the colonies, and education was more common in urban centers, where wealthy individuals could afford tutoring.
Lockridge estimates that female literacy in late 17th century New England rose from 31 percent to 48 percent—roughly half the rate of males. Again, these rates would be lesser in the Southern Colonies. Lockridge's estimates are of white males and females. Slave populations must also be taken into consideration, as slaves were illiterate. In late 17th century Viriginia, for instance, 40% of the entire population was made up of slaves. The slaves were aware that literacy could be the start of freedom, and historians have noted a tradition of slave narratives in which literacy is a central ambition.
https://www.history.org/foundation/journal/winter11/literacy.cfm