West towards Tangier
The ferries from Ceuta to Algeciras are marginally cheaper than from Tangier (maybe 7 Euros less), but it's much harder to hitchhike on them as they carry less cars than the ones from Tangier. Chances are good you won't find a ride.
South towards Tetouan
You might get a lift south, but probably only after you've cleared the border which is about 3.5km walk from the ferry terminal. On the other side there's a place called Fnideq from where it's not far to Tetouan.