Hi Katt, if the bus you’re planning on taking is like those that I’ve taken to out of Santiago to numerous destinations, I believe you’ll need to go down to the bus station to catch it. The new station is right next to the train station. From where you’re staying, it’s a short 10-15 minute walk. Very easy to find. I recently took a bus to Muxía. For that particular trip, tickets were only sold at the station the day of the trip. It may be that an advanced ticket can be bought online. I’m sure someone here on this Forum would know if that is possible.
It’s an easy slightly downhill walk to the station(s) area. After you cross the road to the station - just up the steps and over the train tracks down into the bus station area. You can arrive early if you’re afraid of missing it. Grab your ticket from the ticket window and if you’ve allowed time - there is a great cafe for a snack or café con leche or whatever you’d like.
Edit : @Grousedoctor
Yes., it was a bus to Múxia for me too late may this year.
There was a queue for the ticket then., so @katt it would be sensible to allow enough time in case of a ticket queue.
It was a little confusing (for me anyway ) getting to the right departure stand below. Just note the bus number marked on your ticket - your arriving bus will have that number. Together with a few other passengers (pilgrims); we climbed aboard the bus that arrived at the correct stand at the correct time. Driver set us straight. (We got off that one) - Just because it arrived at my ticketed time - didn’t mean it was my bus (we felt a bit stupid). The busses can be running behind.
You can purchase your tickets at the Monbus website. It has an English Language site. I checked it out and to find the route from Santiago to Sarria instead of searching on the homepage click on routes and ticket offices and search from there. Save the worry and hassle of buying a ticket at the station.
This is the link to the route and ticket office page: