I consider South Baja as Loreto (which is still a 4 hour drive from La Paz), La Paz, Todos Santos and Cabo San Lucas and San José del Cabo.
The two times I drove down the peninsula were in winter so this was the warmest part of the trip.
Loreto is a town on the Sea of Cortez with a nice mission and friendly plaza. The food is much better and than what you can find north and their are great islands one can visit to see whales and dolphins. A fun little town to spend a couple of days without getting bored.
La Paz is a bigger city compared to what is up north. It has plenty of restaurants and beaches one can enjoy. There is the island where one of the Pirates of the Caribbean scenes was filmed (Isla del Espiritu Santo- Island of the Holy Spirit) where you can swim with seals and fish. Watch out for the jellyfish!
An artsy town with a world famous hotel, Todos Santos is a must see. There, one can have a drink at the Hotel California, which is where the Eagles stayed and wrote the very famous song. The town has many good restaurants and art shops.
Cabo San Lucas and San José del Cabo make up what is known as Cabo, the southernmost tip of the Baja peninsula. Cabo San Lucas is the party town where one cannot walk around without being hassled to try a free tequila shot where as San José del Cabo, still pretty tourist oriented, has a more home feeling. It’s the quiet Cabo.