I'm fairly certain that 11 AM is always the earliest on the Classics. I believe only the Dream and Fantasy have a first PAT at 10:30.
When we sailed out of PR last year it was so chaotic. The port was a complete madhouse. We arrived at 10:30 AM (11 AM PAT) and waited outside in a snaking line for 45 minutes just to drop our bags and get into the building (it was all one big line and they took our bags from us at about halfway through the line). It was such a crazy setup. We've embarked from PC, Vancouver, Miami, and Barcelona and this was far and away the longest and most crazy check-in process. We've decided this year to do a little sightseeing at one of the forts in the morning and arrive later, around 12:30 or so, to see if it's less crazy.
According to my notes, they began boarding the first group at 11:45 AM.