Príncipe is tiny — the main road from Santo António to the southern end of the island is under 20 km — but the terrain is steep and rutted in places. The best way to get around is to hire a 4WD with a driver for the day, which most accommodation can arrange for around €40–60. Shared taxis (táxi colectivo) run between Santo António and Porto Real for a couple of thousand dobras per person; ask locally for the current rate.
Walking is practical in and around Santo António, and between the town and the nearest beaches. The forest interior is a different matter: without a guide you will quickly lose your way on unmarked trails. The Fundação Príncipe can connect you with local guides who know the paths to Pico do Príncipe, Pico Papagaio, and the deeper birdwatching sites.
Bike hire is occasionally available in Santo António — ask at your guesthouse — but the hills are serious and the roads are rough, so this suits fit cyclists only.