Was in Madrid recently and found the metro quite easy to use. From the time I landed in Madrid, I…read moreimmediately found my way to the Metro and headed directly to the City Center.
From the airport, you'll take Line 8 to Nuevos Ministerios and then connect to wherever you needed to go. Line 8 is one of the few where the announcements are also in English. The connections were quite easy to maneuver in my opinion.
For me, I took Line 10 to Santo Domingo and then Line 3 to Callao and ended up near my hotel. Very seamless process. A tad bit of walking underground, but that is to be expected outside the US.
I found that the 10 trip is the most efficient deal for a 3 day stay.
The signage is pretty clear in my opinion. I think it's easy for any foreigner to manage manuevering, granted they've had some experience navigating the metros in their local cities.