Where are you boarding?
Your boarding time will be in your documents and may change. Some cruisers with 4*or higher, Neptune Suites, Club Orange have Priority Boarding which seems to mean nothing these days. The issued boarding times were implemented to spread out arrivals in order to reduce crowding and lines as people arrive at the port. That and fewer cruisers seems to be working to avoid crowds except for those travelers who arrive by the bus load.
If you have to check out of your hotel, or if you arrive by airline go to the port and just get in line. Nobody is going to kick you out unless you don’t have your proper boarding documents ready.
Our Vancouver boarding documents in two weeks gives us a 10 a.m. boarding time. In March the ship in San Diego didn’t even start boarding until closer to Noon and our boarding time was 1:30. Most people are finding the boarding process easier than in the past.
The dining room may not even be serving lunch. Don’t ask the stewards, they may not know. Just go to the dining room to see if it’s open.