Hotel San Marcos is located at Latorre 2946, within eye sight of the main bus terminal and centrally located.
Very clean and well-kept.
The room was comfortable, had a comfy bed, clean bathroom, hot water, cable TV with at least 60 channels, helpful and friendly staff. The room is cleaned daily.
Breakfast is included and is decent, consisting of toast, a slice of ham, a slice of pound cake, butter, jam and coffee or tea.
Good value...my single room with private bathroom cost about $15.000 CLP per night (about $2500 CLP lower than what is advertised on the board as you walk in...I read something about a hotel tax that foreigners do not have to pay...maybe that's why).
The restaurant serves a fixed dinner every night for about $3000 CLP. I tried it the first night as was not too happy. It consisted of minute steak, potatoes, rice and a fried egg on top. Also included was a cup of instant cream of asparagus soup and a cup of sweet fruit for dessert. The food was diner quality (bad diner quality) and very greasy. I wouldn't recommend the restaurant outside of breakfast.
The hotel is located on a main road (latorre), and especially if your room is facing the street (as mine was) you get a lot of noise of cars and trucks going by. I wore earplugs, so it wasn't a big deal.
THIS IS NOT A HOSTEL...if you are looking for a fun hostel atmosphere, this is not it. This hotel is frequented by mostly Chileans on business (Antofagasta is mainly a working town)...from the guest book I could see I was the only non-Chilean. But if you are looking for good value, much higher quality over most hostels and a bit of privacy, this is a good place.