Martos in southern Spain

Yes, I know the area well enough, but you can probably find all my knowledge and more with a simple 'google'. What do you want to know specifically?
Martos will be a twenty to thirty minute commute each way by car, taxi or bus from the city of Jaén

Hmmm! I guess I would ask what you would think it would be like to live there? I know we can google this info but something more personal might help. Rents seem to be very inexpensive. I know the area is a leading exporter of olive oil. Is it a farming community? What advice would you give a young man moving there for a year? Do you think there will be many English speakers. And yes I will ask him to respond to you. He may have more specific questions

It looks like an interesting town and he won't be "stuck" there. Trains from Jaen run about 3 times per day direct to Cordoba/Sevilla/Cadiz or 3 direct to Madrid. Buses to Granada run frequently (www.alsa.es).

I have no idea about rents but it seems to me the cost of living is cheaper in Jaén than the other cities of Andalucia, certainly compared to Seville and Malaga.
The only farming that will be seen, unless seeking it out or stumbling on something, will be olive.
I am sixty and I am not sure what I can offer a young man as advice, except, mixing only with English speakers, or an expat community if there is much of one (and I do not seek them out), is not going to broaden his horizons much. Mixing with Jiennenses who may also speak English will. Everyone between teens and thirtyish will have some English whether they paid attention to being taught it in school or not, and/or from music and film.

I'm thinking the rents might be low since the industrial park out on the east side does not appear to be populated sufficiently to be producing at full capacity. It was largely automotive sub-assemblies of some sort, I believe. That, and the good chunk of closed stores, plus the plethora of apartments for rent, would obviously drive down prices. It all probably stems from the economic downturn six years ago or so.

Martos isn't depressed or depressing but it doesn't have the diversity of Jaen, a provincial capital. It does have everything you'd need for regular day-to-day living. Given my druthers, I'd rather walk to work and take breaks in the larger city than commute every day.