Sirius had been hoping Regulus would say what he said. Even though he knew his brother's prejudices were much lessened by his year on the run, he still couldn't help but expect him to come out with one of the filthy M-words every now and again. In response to Regulus' suggestion, he nodded.
"I threatened his address out of him. He didn't want to tell me, but that's Remus for you. I think we should try and get him here. He's safer out of the country, even if he doesn't stay with us for long." Of course Sirius would rather Remus did stay with them, but his recklessness was distinctly toned down from the good old days, and now he actually stopped to think things through now and again.