First 7-day cruise, will I find enough to do on shore without purchasing excursions?

Of course you can! There will be several vendors outside the port willing to sell you anything from shore excursions to tiny trinkets. You can also purchase a map, rent a car or scooter, and explore the areas on your own. All of thise will be much cheaper than the cruise lines offerings. While in port, sse some basic common sense and you will have a safe enjoyable time. For companies that are highly recommended for independent excursions, visit cruisecritic forums. They have 1000s of travelers just like you who like to save money not using the ships overpriced excursions. FINALLY, THIS IS MOST IMPORTANT: WHEN TRAVELING A NON SHIP EXCURSION, KEEP TRACK OF SHIP TIME. THE CAPTAIN WILL LEAVE YOU! IVE SEEN TONS OF PEOPLE CHASING THE SHIP AS WE PULLED AWAY! Enjoy your cruise!