Debbie - I'll add my welcome to LCT to Karen's. I would agree with her, everyone will be happy to just let you move and post and stuff at your own pace. How exciting that you've planned the World Cruise for next year and I'm sure it will be the trip of a lifetime.
Have a wonderful time on the Diamond next week. Oh, I don't know the answer to your question, we've sailed from San Juan twice, both times from different piers, first time was the pier right down in Old San Juan, and my vague recollection is that there were some kind(s) of lockers on the ground level, but it was a really long time ago. The 2nd more recent sailing was from a pier quite away from town and I honestly don't remember any lockers or such. You might contact Radisson to see which pier they sail from and ask them if they have somewhere you can temporarily store your luggage.