The main taxi rank is by the central medina. Fares from the centre to Hammamet Sud are about 5DT.
In high season, tacky tourist 'land trains' chug past all the major hotels between the central medina and Yasmine Hammamet. They're run by different companies (tickets are not interchangeable) and can be expensive, at around 5DT for short trips.
Local buses run approximately half-hourly from Hammamet's centre to Yasmine Hammamet from red-and-white signposted stops.