I live in Tortuguero, so I think I'm a bit biased, but I recommend Tortuguero. It's known as Central America's Amazon, and for good reason. The island has no cars, and you can only get here by boat or plane. I recommend the plane ride on the way out, but the road/river route is kind of fun on your first time in to Tortuguero. You will most likely see three species of monkey, hundreds of bird species, and many reptiles including caiman, crocodiles, the "Jesus Christ" lizard that runs over water, and the magnificent sea turtles that come here to nest.
The great thing about coming at the end of October is that you can have the chance to see turtles hatching, and possibly nesting as well. The season officially ends the 31st of October, but there is always some activity into November, and this year has been very good for turtles.
I would recommend against the all-included packages. They are overpriced and most have sub-par food, plus you have no liberty to decide on your own schedule. The tours are structured and scheduled, as are the meals. There are plenty of dining options in town (including my restaurant!), and several mid-range hostels and B&Bs. Casa Marbella and Hotel el Icaco are two of my favorites, both include breakfast. Lodging in town is simple, but is actually very similar to all but the most expensive all-included lodges.
Just one thing I like to remind people of: If you come during turtle hatching season, you should not, by any means, dig up nests. Some locals try to make money by helping tourists find nests, which they then dig up to "help" the turtle hatchlings, and some even "help" the turtles by carrying them to sea. Both of these activities can be extremely harmful to the hatchlings, so please don't encourage them by paying someone to help you find nests. Even if you don't see them actively digging, sometimes they do that ahead of time and then call the tourists over.
You can simply walk on the beach from very early in the morning and you are likely to see a nest hatching.