Nabeul is near Hammamet and you can get there with the bus. It takes about 20 min to get there from North Hammamet and costs around 1-1.5 TD.
The biggest problem is that the bus stops in Hammamet, especially in North Hammamet are not marked properly. That's why we missed the bus. Actually we wanted to go to South Hammamet with the bus, we missed it because we were waiting for it on a wrong place and then we decided to go to Nabeul instead. It may be helpful you or your companion to speak at least French, if not Arabic, to ask for the bus stop, since the old people in Tunisia speak French and not English for example.
Get into the bus from the last door (not from the first one as you may get used to in Europe) and buy a ticket.
of course there are taxis in and out of nabeul. but the touristic train, is a valuable option, to go to and from hammamet, to nabeul or the others sites at the gouvernat de nabeul. passing thru the center of tunisian towns and be able to apreciate all that on a open air train and really enjoy tunisian scenes and habits. and grab yur camera and take all kind of shots...