Playa San Juan works best as a quiet base for exploring the southwest coast and the mountain interior.
Los Gigantes, twenty minutes north, has the most dramatic cliffs on the island — a vertical wall of basalt 600 metres high running into the Atlantic. The Masca valley winds inland from there, a narrow ravine with a small village at the head; the hike down to the sea is one of the classic Tenerife walks.
Teide National Park, about an hour by road, is unmissable — a vast volcanic caldera with the snow-capped peak of Teide in its centre. You can drive a loop around the crater, take the cable car most of the way up the mountain, or walk a stretch of the lava-field trails.
South along the coast, Los Cristianos and Playa de las Américas are the big resorts, useful mainly for the ferry to La Gomera and for nightlife if you want a noisy evening out.