My favourite place of all to Ride is anywhere in Anaga.
TF21 all the way from Granadilla de Abona all the way through to Aguamansa/La Orotava is fantastic!
TF24 from El Portillo to La Esperanza is also brilliant.
The loop that goes from Santiago del Teide, to Masca, El Palmar, Buenavista, Garachico & El Tanque is pretty spectacular. Unless you're a masochist, it's best to do the this route in the clockwise direction stated here. Otherwise, there's one helluva climb out of the Masca village all the way up to the lookout not far from Santiago del Teide.
TF28 to Guimar/Arafo is a good, undulating road apart from just a couple of km in the beginning (or so I'm told). The first part of this road leading out of Los Christianos is busy, so expect traffic.
The climb TF245 up from Arafo to Bosque de la Esperanza is possibly one of the best on the island. Sunny + great road + zero cars.