Even though the law states otherwise, yes, they won't let you apply for a DR driver license unless you can present a cedula (national ID card). Cedulas are only given to legal residents (a 8 to 18 month process) and nationals.
You can drive on your foreign driver license for 6 months. After that you would have to leave and re-enter the country to be able to drive another 6 months, a routine many who applied for residence had to perform to be able to drive legally while waiting for their residence papers to be issued.
Upon asking around for a solution, you may happen to be offered "help" in form of a "facilitated" license, sometimes even from officers right at the driver license office.
Never be fooled into believing that these would be LEGAL, and that in case of an accident the whole think would not blow up at your face, resulting in you being thrown into jail and out some substantial amounts of money. DON'T DO IT!
... J-D.