It's fine to ask now. I'm a hiring manager and my recruiter always discusses it during the initial phone screen. For the exact reason you mention- we don't want to waste anyone's time.

A former coworker asked for my resume and sent it in to his company's HR departments. They reached out to me and invited me in to meet with them with a specific job in mind. From the job title and department I can pretty safely guess the job they've approached me about would be a 20-30% pay cut, which I absolutely cannot do. Since they approached me about the job - when can I bring up the salary range question? I don't want to waste their time or my own interviewing for a position that I would never accept.