The most sustainable way is to use the TRAM (streetcar) of FGV, which has 4 stops along the municipality: Altea, Garganes, Cap Negret and Platja de l'Olla.
If you prefer to arrive by private vehicle, you will take the AP-7 (currently there is no toll) and the N-332. My advice is to use the parking lots a little away from the center, as detailed in this map with the points of interest of Altea.