Buses, taxis and car hire - what actually works.
The green TITSA buses are cheap, reliable and cover the island. The 40 and 111 link the south airport with Los Cristianos, Playa de las Americas and Costa Adeje; the 110 runs to Santa Cruz. Pay by contactless card or phone on board - fares are roughly 1.50 to 5 euros depending on distance. A ten+ travel card makes regular rides cheaper.
White, metered and honest. Airport to Costa Adeje is typically 25-30 euros. For a fixed price and someone waiting with your name, pre-book a transfer instead.
The best way to see Teide, Masca and the north. Book ahead in school holidays. Pick a firm with a full-to-full fuel policy, photograph the car at pickup, and check the excess - cheap headline prices often hide a large one. You drive on the right; motorways (TF-1 south, TF-5 north) are free and good.
Fines for speeding are real and cameras exist. Mountain roads (Masca, Teide) are narrow with bends - fine at a calm pace. Parking in the south resorts is easier than in Santa Cruz.
Almost all UK flights land at Tenerife South (TFS). Tenerife North (TFN) serves Spain and the islands. Check which one your return flight uses if you island-hop.