Depending on which route you follow to arrive at Santiago, way markings once you hit the city can be daunting. It is my understanding based on what many people have told me over the past few years that part of the reason is political.
The current head of the concello (mayor of the city) holds quite a bit of antipathy towards the Church, writ large. Sometimes, it amazes me that he and the concello do not respect the effect of pilgrims more. But, heck, it is Spain. Be it far from me to get involved in local politics...
I was reliably informed that, because the concello / city approved blueprints for the newly renovated Pilgrim Office at Rua da Carretas 33 read, "International Welcome Center for Pilgrims," he directed appropriate city departments to erect directional signs stating just that and nothing more, and in Gallego (Galician dialect), not Castellano (Standard Spanish.
So, try as you might to find the Pilgrim Office or the Oficina del Peregrinos, on a map or smart phone app. You will likely not find it. In 2016, Google Maps did not even show it. It does now.
For now, the best way to find the Pilgrim Office and the end of ALL the Caminos is to seek the Cathedral. The FRONT of the Cathedral is the West side. In early Christendom, all churches were aligned so the altar was facing more or less towards Jerusalem, or towards the East. The front of the Cathedral, or more precisely the bronze plaque in the center of Plaza Obradoiro is the geographic point from which all distances are measured.
So, and as a collateral point of interest, when I was last at Santiago, I used my Apple Maps app to calculate the distance from that bronze marker to my home address in South Florida. According to the app, the exact distance was 6591 Kilometers, as the bird flies.
I am even toying with using this fact to establish the "Camino de Playa de Palmera" (Camino de Palm Beach) to use this distance for off-season training purposes. My thought was to subtract the distance from La Coruna or Ferrol, then train each day to cover the distance across the Atlantic from Palm Beach, FL. From La Coruna or Ferrol, I would pick up the land trail into Santiago.
At an average of about 25 km per day, it will take 260 calendar days to "walk" from my home to La Coruna or Ferrol. At 30 Km daily (Florida IS very flat) it would still take about 217 days.
We shall see...