Monte Carlo

Yes, everything is very walkable.

Be sure to get your passport stamped. I have to say it is the coolest stamp I have in my passport. There is by a post office on the hill where they have that changing of the guard. The details are in the RS guidebook. Trust me, you will like the stamp!!

are you sure that your ship is actually docking in Monaco? Many ships, especially larger ones, anchor off Villefranche sur Mer and tender passengers ashore there. If so, the station in Villefranche sur Mer is a reasonable walk from the tender docks and then a short train trip to Monaco. Once in Monaco the delight is the walking. Outside the Casino is a garden which my wife and I make a bee-line for everytime we are in Monaco (most years). I keep trying to duplicate photos made years ago but there is always a subtle change.

You will either dock or shuttle in at M Carlo. A few years ago M Carlo built a cruise ship dock that will handle two cruise ships. If more than two in port then the ships anchors off shore and shuttle in.

I liked Monaco more than Rick Steves does (to be fair, many others share his opinion). I enjoyed the Aquarium, the exhibit of the Grimaldi's cars (they are adamant that it is not a "museum") and the Jardin Exotique, with its lovely plants and views. It was also interesting to see that the castle is on an actual rock, which would have been easy to defend. Monaco was notably cleaner than other Riviera towns. A day pass for the local Monaco buses is €3, and very useful (it's €1 per ride otherwise). While Monaco is very small, the hills and water mean that you can't always get from one place to another easily. You can get from the cruise terminal to the casino on foot easily (if, as said above, your ship actually docks in Monaco). Since you are on a cruise, you will find Rick Steves Mediterranean Cruise Ports invaluable. He will have lots of information on your ports, including how and whether to do them yourself or take a port tour. No expensive tour is necessary in Monaco; if you want an overview, you can take a local bus tour with commentary (I think it's about €10).