Vilankulo is very spread out. For a taxi, try contacting Sr Eusébio, or arrange one through your hotel. Occasional chapas run along the main road, but not out to the beach places on the northeastern edge of town, and not to the airport. Chapas to Chibuene (Mtc20, 30 minutes) depart from just down from (west of) the old market. They can take a long time to fill; for about Mtc100, drivers are usually willing to leave when you're ready. The chapa terminus in Chibuene is at the main T-junction. For Archipelago Resort, ask the driver to drop you at the turnoff shortly before the T-junction.
At night, it's advisable to take a taxi in the area near Baobab Beach Backpackers, to/from the Maputo bus terminus, near the old market and anywhere near the beachfront.