Here are the dividend options as shown on the SAN Home Page:
1) Receive new ADRs (this is generally the default option, no Spanish tax withheld), or
2) Sell rights in the market for cash (no guaranteed price but no Spanish tax withheld), or
3) Receive a fixed amount of cash from Santander (Spanish tax withheld at a rate of 21%).
As I hold these shares in my IRA, I elect option 2) above and get cash. It seems to work well. I get cash and do not have to pay any tax or commissions. GLTA