Stay in La Marsa
All necessities are within a walking distance. The main street area of La Marsa is within 5 minutes walk.
I would say the neighborhood is a bit too popular for my liking, but it really gives a sense of local Tunisian life and local people.
The bus station is within 5 minutes walk, but taxis are available everywhere. If you're lucky, you can find one as soon as you walk out the door!