Depends on the time of year. If you come during the dry season, you can sit all day and night on the beach. Take a canopy tour through the jungle, repel down a waterfall, go on a nature hike and see all the animals. Relax at the bar and party if you want. If you rent a beach house you can also cook your own meals which will save you money. Cruises can be expensive, but they do take you places and your meals are included. You won't be able to enjoy the night life on the island or whatever country you visit. You are always on the ship during the night. You will be more catered to on a cruise. Coming here, you can set your own schedule and pretty much do what you want, when you want. There are a lot of extra expenses that you can incur on a cruise that you will have to pay before you leave, they can add up quickly. Splitting the cost of a beach house will probably be a lot cheaper, giving you more money to do more. Costa Rica is a beautiful country with amazing people, you would love it here.
Costa Rica has a lot to offer... but if you want to "sit on a beach and bake in the sun" there are better options than Costa Rica.
Costa Rica is great if you are into surfing, or eco-tourism, such as exploring rain forests, volcanos, etc.
If you want to sit on a beach and bake in the sun, look at an all-inclusive resort in the Dominican Republic, Mexico, or the Bahamas.
Some friends of mine and I are looking for a relaxing 1 week vacation in a tropical climate where we can sit on a beach and bake in the sun. One of my friends doesn't want to plan anything, so he's leaning toward a cruise. My other friend and I are leaning toward Costa Rica because there is more variety and we are thinking about renting a beach house. Also, she gets sea sick. Anyone have personal experience with either?