I faced this very issue last week in court. I sent certified return receipt mail to opposing side. The opposing side did not sign for/pick up this mail.
At my hearing, the Judge went straight to the issue of service before even looking at any of the arguments. I had my certified receipt and a printout of the USPS tracking status.
I presented this to the bailiff/Judge and before the bailiff could even get it in the Judge's hands, she said, "where's your green card?"
The other side was able to get a continuance just for avoiding picking up their mail, and I was lectured by the Judge for not serving the other side properly. Nevermind that I had followed the civil procedures and paid for an official sheriffs' summons 4 months earlier, nevermind that nowhere in the state civil procedures does it require return receipt, nevermind that I already had the motion down on the court's calendar 4 months earlier, and nevermind that both court clerks came running out of court to tell me point blank that the Judge was wrong and I could appeal her decision.
What I got from the Judge was, "If you want to be your own attorney as a pro se, you need to learn the rules of civil procedure."
Two attorneys came out of the courtroom to tell me not to worry about it, because I was still right in my service.
The point is, attorneys can get away with just regular mail, or certified mail, or maybe they don't need a green card. But my experience has shown that pro se's are held to a different (higher) standard because Judges are inherently questioning the pro se litigant's knowledge/ignorance/misunderstanding of the law.
Lecasbas is dead on when he says to DV early and repeatedly until you get the green card before the 30 day window. I have taken the position to assume that the same difficult Judge will review every action of mine. If I don't have that green card, I can't reliably move forward with litigation. Certified Return Receipt seems like it costs more, but it leaves no room for confusion in Court. When you add in things like court continuances, certified return receipt mail is a bargain.