In Sousse we researched the best way to get to El Jem for the day. The verdict - use the louage. The French word literally means ‘rental’ and refers to the shared-taxis that travel between towns and cities.
We took a taxi to the louage station, and paid 3.45 Dirham each for the trip. In Sousse the tickets were issued by computer, and we were on our way in 20 minutes.
The drive was fast, less than an hour, with some lairy overtaking, and the louage station in El Jem was only 10 minutes walk from the Colloseum.
Getting back was not so easy. There were no louage to Sousse in evidence. Any vehicle which arrived was mobbed by prospective customers. The lack of system contrasted with the organisation in Sousse! It seemed likely that any loage to Sousse would have more prospective passengers than seats. We adjourned the search to tale lunch. Instead we took the through train to Tunis, getting off at Kazaa Seghira and taking a taxi back to Sousse.
To see spots of interest for us tourist and have coffe/meal, no transportation is needed. Feet will do quite fine even for elder people as:
1.from train station to amphiteatre takes less than 5 minutes
2.cofffe shops/restaurants are located along the amphitheatre
3. archeological museum is some 15 min. remote if you take a slow walk, that is also a good suggestion to see the place, and sense it better
NOTE: around amphitheatre: to me it took 1 hour, and I could have stayed there longer!
If you are in Sousee, El Jem is easy reachable by local train. You will have exact time you need to sense the place and snoop around in the case you leave Sousse at 8am and check the return at noon. At the station you can get the schedule.
The cost, 1st clas, to El Jem and backwards: 8.500 dinars
Duration of journey: 50 minutes
On the way you will see olive tree plantations, a bit of Sousse city, and cactuss herbs used as a 'fence' fpr the gardens. Not spectacular, but IS part of Africa :)
You can easily cover El Jem without any means of transportation but your own feet. . It is a very small place, and the only things you probably need to see are the huge amphitheatre and the few stones that remain from the Roman villas. Still, it may be hot, and if you come to town in a car, you will not need to leave it - just stick with it: you'll have no problems with parking space .