The english is not much different at all in the south,
but there is certainly an accent that makes it sound a little different.

some examples of differences...

e.g. instead of saying
"Everyone is invited"
a southerner would say
"Y'all are invited"
Y'all being short for "you all".
Y'all is definately slang.
Idiomatic expressions will differ slightly,
but this probably true of any area in the world.

In general I would compare the difference to
listening to a person from London speaking English
compared to someone from Washington DC.
That is to say, the English is not really different at all,
but to a non-native speaker it certainly sounds a little different.