My wife and I visited the Arenal Observatory Lodge which is beautiful to say the least. They have the best view of the volcano and of Lake Arenal by far. But, on a sad note, we were there during the rainy season which kept us from seeing the acutal top of the volcano.
If you in the area and hiking down a jungle trail to see a waterfall, be careful where you step. Not only are there spiders and other biting insects, there are also snakes. We stumbled across this one just by accident.
While walking along one of the paths, we noticed these big ant hills off to the side, so Hubby had to go and investigate. On our first day there, the guides warned us to always tuck our pant legs into our socks, so the ants wouldn't crawl up inside your jeans. You'll notice that Hubby follows recommendations really well.
I believe this is the Spanish equivalent to 'over the lips, past the gums....', It was taught to us by the bartender at the Eco-Lodge, as he somehow convinced us to try something called 'Guaro'. We've been married almost 14 years, and still have the bottle in our liquor cabinet, waiting for another unsuspecting guest...
One day, while walking back to the Lodge from Coter Lake, we noticed 2 other guests looking at something on the road. As we approached, we saw this guy, just laying on the road. One of the others ran to the Lodge to get one of the guides, who just happened to be a herpetologist. With 2 sticks, he manouvered it into a bag and released it far away. He confirmed it was venemous.
The main danger of writing tips and pages on Arenal is that you will put them in the wrong place.
If you want to be near the volcano and the lake,
Santa Elena 3.63 km / 2.26 miles
Laguna de Arenal 4.08 km / 2.54
Tilarán 1 11.78 km / 7.32 miles
That is the OTHER Arenal.
Arenal Volcano is fun to go to. The majority of people will see a few rocks tumbling down at night, maybe hear some rumbling if their hotel is close enough. Just remember that it erupts about daily, and a few tourists have been killed by wandering too close before an unexpected explosion. However, don't let that stop you from spending the night in La Fortuna. Two reasons - the smoke and gas haven't ever gone to the La Fortuna side (as far as they know) and the town itself is nice. Definitely worth a stop.
Arenal is a fairly safe destination, and I never felt threatened. But opportunity make the thief, so just be smart. Don't leave valuables in the car, or your luggage visable. Don't speed.
Use the hotel safe if they provide one. Have a copy of your passport in case you lose it. San Jose I hear is a much more dangerous destination where one should pay close attention.
The Lonely Planet travel guide provides some good general safety tips.
As you're walking through the rainforest, you will see many things which may fool you! I got a real scare when I saw what was on this tree, until I realized it was a vine, not a boa constrictor!!