Walking is the preferred mode of transport in Mieres. Mieres is very long, but not very deep since it is bordered by a mountain on one side and the River Caudal on the other. Since most of the shops are centrally located you don't need a car to get around. Whether you plan to shop, eat or enjoy the pubs, you feet should provide you with the mobility you need. On the periphery of town are the "projects" (areas where you don't really need to be) so as long as you plan to stay in town, you won't need a car or taxi.
It is over a one mile walk from the train station to in town, but it is an easy path to follow. From the train station you cross over the foot bridge and make a left onto Doctor Flemming. Make the next right onto avenida Manuel Llaneza and follow several blocks to the shopping area. Avenida Manuel Llaneza is one of the main arteries in Mieres. Of particular interest is calle La Vega, a pedestrian mall of shops and pubs. La Vega is a right off of Manuel Llaneza.
Follow the link for a bigger map to zoom in on map.
To get to Mieres you can take either the RENFE or FEVE train. The train is very cheap (under $2.00 from Oviedo). The link below is to the RENFE Cercanias Asturias website, which gives specifics on destinations within Asturias (in Spanish.) The RENFE train was my preferred mode of transpo in Asturias. The FEVE train makes much more frequent stops but travels longer distances.
You can also take the bus to Mieres and it drops you a little closer to center city. The only problem it that it actually drops you at a more confusing location. The bus trip is only 20 minutes from Oviedo, compared with 30 by RENFE. The bus is a bit more expensive, was very cramped and made me carsick. I preferred the train with offered great visitas and the opportunity to stretch my legs.
Mieres is located right of of "interstate" route 66 which runs from Gijon in the north of Asturias to Leon in Castilla-Leon. This is the quickest way to get to Mieres. It is very scenic with lots of tunnels (typical all over Asturias.) This is the tunnel on the highway next to Mieres.
This map is of the city Mieres del Camino and the region Mieres. This will give you an idea of it's location relative to some of the smaller towns nearby and RENFE train stops.