I bought my Tarjeta Dorada at the Malaga Renfe station in May. I just needed to show them my American Passport. The card also is good on the Cercanias. Below is the info on the RENFE website. It is a very good bargain.
People are entitled to the Tarjeta Dorada Card if they are over 60 years old, or are in receipt of a pension being over 18 years old, with a permanent, total or absolute physical or mental impairment or severe disability that has been officially declared, or have a level of disability equal to or more than 65%. For this last group of people, the words "AND TRAVELLING COMPANION" will be printed on the card, which will allow another person to travel with the same terms of discount.
The Dorada Card is valid for one year and can be requested at Renfe stations, ticket offices and travel agencies for 5 Euros. There is also the option of obtaining a Tarjeta Dorada linked to credit and debit cards issued by some banks.
25% to 40%. Dorada Card holders, 25% from Monday to Friday. 40% Saturdays and Sundays.