Let's see what I can do here to answer your questions.
On disembarkation, it varies dramatically by port, and whether you dock or tender. In Cozumel, likely you can be off the ship within 30 minutes. In Grand Cayman where you have to tender, it could be closer to an hour to 90 minutes before you're ashore. Normally you can do it within an hour, but best to leave a bit extra time. Those with excursions purchased through the cruise line have priority tendering.
Keep checking the Personalizer. When they assign your cabin, that GUAR will change to a particular cabin number. There's no way to tell now what it will be, just that it will be category FF or higher.
Princess tends to upgrade people into higher category cabins rather than sell them at the dock. If you want a balcony, ask your TA to keep an eye on the prices, and you should as well. Often the last round of upgrades begin at about 2 weeks out, so I'd try to purchase before then. After that, there likely won't be an opportunity. Also, there aren't any last minute discounts on upgrades on Princess.
Make sure your TA puts in your record that you're celebrating an anniversary. If you do end up in PC dining, ask the Maitre d' before the date what you need to do to ensure you get the celebratory cake. Likely he'll just ask for a reminder when you're seated that night, but make sure you don't just presume.
Coffee is pretty bad. It's usually moderately acceptable through room service, but truly horrid at the buffet. If you're a coffee fanatic, bring your own. There is a small refrigerator which is perfect for half and half. One other secret, there's a small coffee bar on the Promenade deck just off the atrium. That's the best place on the ship for coffee.
Your steward can provide bottled water in your room. When you arrive there will be one bottle for purchase and it's a simple matter to ask for more. You can also bring some aboard if you prefer.
Hope that helps!
