Oh, sure, come back as many times as you'd like. We're all glad to help you.
"continue in the pattern, at the same time, on the second round dec 1 st on the left side of each pearl section by p2tog. Repeat the dec on every 3rd round on the right and left side of each pearl section alternately a total of 20 times"
The pattern wants you to alternate the place where you do the decrease: p2tog on the left and then 3 rows later p2tog on the right until you've done a total of 20 decrease rounds.
Love to see a picture of your finished poncho, too.