Public transportation is very good in Spanish cities, most of which operate efficient bus and rail systems. Public transportation is convenient if your sphere is within a major city. 

Within Spain, the railroad is state owned and is referred to as RENFE.  Their fastest trains, the AVE, are among Europe's best.  The RENFE provides service to all major cities.  To travel to the smaller towns, it will be necessary to take a smaller line, such as the FFCC and/or private railways. 

There are also a variety of local, short-distance trains called tranvía (also a tram). Suburban commuter trains (cercanías) are second class only and stop at all stations.

If you wish to take a taxi, be sure it displays a taxi license, as they are strictly governed.  A green light on the taxi indicates that they are free, and you just have to flag them down or stand at a designated taxi stand.  Be sure to clarify the price, although meters should be in every taxi.  A 5-10% tip is customary. 

Metro lines are found in Madrid, Barcelona and Valencia. They’re the best and fastest way to move around these cities and can be surprisingly empty during rush hours!   Special day rates are available, as are weekly and monthly passes.  A subway map can be obtained at each metro station.