Half Moon Bay is 45 minutes from San Francisco by car. The standard route is south on Interstate 280 to Highway 92 west, which crosses the Santa Cruz Mountains in a twisting fifteen-minute climb before dropping into the coastal plain. On summer weekends the road backs up in both directions; midweek and off-season it is empty.
From SFO airport, the drive is 35 minutes via Highway 380 to 280 to 92. There is no rail or BART service to the coast. SamTrans runs an infrequent bus (route 17) between Half Moon Bay and Pacifica BART, and route 294 connects to San Mateo; both take roughly an hour and are not practical for anything other than a long, leisurely visit.
Coming from the south, Highway 1 along the coast from Santa Cruz takes about two hours through Pescadero and Pigeon Point. It is one of the great California drives but you should not be in a hurry. Cyclists ride it as a multi-day tour stop.