Santiago de Compostela is walkable, although it’s a bit of a hike from the train and bus stations to the centre.
Up to 23 Empresa Freire (981 58 81 11) buses run daily between Lavacolla airport and the bus station (€1.70). About half of them continue to/depart from Rúa do Doutor Teixeiro, southwest of Praza de Galicia. Taxis charge around €15.
Bus 6 runs every 20 to 30 minutes from Rúa do Hórreo near the train station to Rúa da Virxe da Cerca on the eastern edge of the old town. Coming from the centre to the train station, it stops on Rúa de Santiago Leon de Caracas. Bus 5 runs every 15 to 30 minutes between Praza de Galicia and the bus station, via Rúa da Virxe da Cerca. Tickets cost €0.85.