I would take the deal, however, I would ask that the sterilization procedure not be done and that I instead be place under strict supervision. If too many people become immortal and are unable to reproduce, and many of them die in crimes or wars, then we are going to need to reproduce to get the population back, and if immortals are the ones that survive, we are screwed.
Hence, either no sterilization treatment, just strict monitoring, or a fully and easily reversible sterilization treatment that I know, and have the equipment to, perform if need be, but once again, I am under strict monitoring.
If the answer was no, I would ask if I could deposit sperm in a sperm bank for if the need ever arose, and take the treatment regardless of the answer.
I have no need to have children and honestly, I would not want any until the world is a better place for them.