Is it proper for defense counsel to go into the sex offenfer registration requirement during voir dire to explain the consequences of a guilty verdict in a sexual assault since there is nothing that a jury can do to affect whether or not the defendant must register?

NO

"There's nothing a jury could do to affect the requirement to register" -- they could acquit if they have a bias or prejudice against the law that requires registration. I'd like to know if I'm going to have a jury nullification issue. Since registration is part of the "law applicable to the case" the defense atty may be able to convince the court to let him go into it - I have had courts go either way on this. Plus, jurors who express no problem with the lifetime registration requirement have seemed to me to be more state oriented / less likely to acquit

For what its worth, I agree with John. It may be a law ancillary to the case but courts have specifically held that registration is not punishment so it is not relevant to any issue for the jury. If a jury is inclined to nullify over registration, there are much bigger problems with the case.