Paul, when the threat of frost is over, go ahead and prune it down to the new spring growth. I've pruned mine down to about 6 inches and it comes back nicely. Our greggiis get woody after a few years here, possibly because I haven't been good about always pruning them at the right time.

Jen

Paul I cut all my greggii back in Feb. They are doing great and full of blooms.

Pruning salvia greggi by a third of plant volume 2 or 3 times a year depending on when last and first frost of season. First prune shortly after last frost then again 2 to 3 months later and a 3rd time if you have 2 to 3 months left before first frost. You want it to harden off before first freeze of season. Hope this clarifies some of the variations on pruning time and timing.
David