Golf: Try contacting the Los Gigantes Golf Society ( Kev, Paul, Andy will help and are always keen to get visitors in a game and are very helpful) usually found in Bar Arena ( once was Harry's Bar ) or Bamboo Bar in Los Gigantes. They'll fix you up with a game or two.
Local Football: Ground opposite the main entrance to the Playa de la Arena hotel ( local team is Escuala Municipal de Futbbol de Santiago del Teide, run teams from kids level to senior standard ), great facilities, and have a beer while watching a game from the little bar in the corner of the ground. CD Tenerife struggling and missed out on promotion again last season. Try the English Supporters Club, Amarda Sur based in Playa las Americas.
Other Sports: Try the Sports centre a little further up the road from the football ground, indoor swimming pool, squash courts, sports hall for 5 a side football, gyms etc.