I’ve been on several cruises. Dollars are universally accepted. In Cozumel, I did a snorkeling excursion and a horseback ride through the Mayan ruins. The horseback excursion was really nice. I haven’t been to Costa Rica or Panama, though.
Regarding the ship, I don’t think you will be bored. You can sit out on the deck, attend art shows, read, relax, gamble, drink, and people-watch. Personally, I like heading as far forward on the ship as I can and watch the flying fish leaping away from the bow. You can also look for dolphins.
When I am on cruises, I find that doing nothing is the hardest thing to do, but if you can, just look at the water and think deep thoughts. It might be the best thing you can do.
Normally, when we have cruised, we have gone with family, which means we have dinner together each night. On our cruise last year, it was just my wife and me. We enjoyed getting to know our table mates each night. Plus, there is something so very cool about having your waiter get to know you by name and your dining preferences. It is a very special touch to have him greet you by name (“Mr. Bob”) as he guides you to your seat. Makes you feel special.
I really enjoy talking to strangers and getting to know them, and I find that having breakfast and lunch with strangers is an awesome way to learn interesting things.
I speak a little Indonesian, so I enjoy talking to the Indonesian crew members in their own language. They get a real kick out of someone making the effort.
On our last cruise, I met a guy who was absolutely fascinating. He was a retired AP photographer who was now in the computer forensics field, and he had some awesome stories. I regret not getting his email address, because he was an absolute hoot!
Oh, and take a nap in the afternoon, if you can. Do it at least once. It will recharge your batteries like you wouldn’t believe!