Traveling to Tortuguero is an adventure in itself. You cannot drive there, so water taxis from Caño Blanco (near Parismina) are a must (unless you decide to fly directly into Tortuguero). Most hotels will include transportation in the price of their stays, and this is highly suggested! You'll first travel from San Jose to Siquirres via the Limon highway. On the road from Siquirres to Caño Blanco, you will pass several banana plantations, and see how bananas are grown, picked, and processed for export. The banana "trains" are elevated tracks along which bananas travel from rolling hooks; an interesting sight, especially when someone is driving one. (Personally, though, upon learning how much pesticides are used to grow the bananas, the trash that is generated, and the exploitation of the workers, I decided to go organic after the visit.)
At Caño Blanco, you will leave your car or bus and board a water taxi. (Tip: Sit near the front of the boat to avoid spray from the river and less wind blowing in your face.) It takes about an hour and then some to get to Tortuguero, and you'll probably see a variety of wildlife on the way there (we saw a three-toed sloth in a tree, the taxi driver politely stopped the boat and let us all get a good view of it).
Though manatees inhabit the waters around Tortuguero, you wouldn't know it the way the taxi drivers speed around. In fact, on the way back from our stay, our driver hit something in the water (I can only hope it wasn't a manatee), and only after that decided he'd better slow down. There is a speed limit on the water, but no one seems to take any mind of it.