Yes, quite a few... Make sure sure you get to Arenal, a volcano that is in constant eruption. There's a great hot springs at the base. I would also suggest that you take a raft trip down a river. It's even better if you fall in since the water is so warm and clean. Don't spend much time in San Jose, like most CA capitols, it's a dirty, noisy armpit. Rent a car and get out and tour the country. Stop in the small towns. Talk to people. Play at little footy with the locals at dusk. Ah, I wish it was me going.
Re: Yes, quite a few... I am actually going with a group of about 800 college students, so I'm sure it's not going to suck.
Pura Vida Get the hell away from all the college kids. Seriously, if you want to really enjoy and get a real feel on how Central America is, I would suggest separating from the rest of the pack and take one or two people that you can get along with. Pickpockets are drawn to large tourist groups. Plus, the logistics of trying more than 3 or 4 people to agree to go to one location can grate on one's nerves. Turriablo is a nice place to visit as well as Monteverde Cloud Forest. Puerto Viejo on the Caribe side is nice as I spent a bit of time there working on a turtle conservation project. Manuel Antonio Nature Reserve is nice to go to. It has been a bit spoiled since all the animals are used to being fed by humans. Arenal is already mentioned. A huge surf spot on the Pacific is Quepos or Jaco (not sure which though). There were a lot of tourists there, so it spoiled it a bit for us. The Nicoya Peninsula is nice to trudge around for a few days. It may have been Jaco. And take the bus if you are adventurous. You won't soon forget it, if you don't get your pack pinched! If you really like Purto Viejo, I;d suggest going over the border to Panama in a place called Bocas Del Toro. There is no surfing there, but the atmosphere is very laid back.
I spent two months, in between my junior and senior year in college, and also when I graduated I spent about 2 weeks there. If you want to know of places to go....you can pm me. I have been through most of the country. You should enjoy it immensely. If you get out near the Limon province (east coast), try to make it out to Tortuguero. It is one of the largest breeding groups for sea turtles, and also has a fun night life.
About 4 of us are planning on renting a jeep and just cruising around the backcountry for 2 or 3 days, going Jeepin'. The last time we did that in Mexico we almost killed ourselves on 3 separate occassions, but it was the most fun i've ever had.
Every time the bus stopped in Limon, the bus driver told us under no circumstances would he open the bag compartments. Apparently, Limon was a hotspot for pickpockets. Every time, we went through that city the locals on the bus would say that this was a bad city for thievery. Once a person got on the bus and started rifling through a friends' belongings. When he got back on and saw what was happening, he was pretty heated and just yanked his wallet out of his hands. The guy nonchalantly walked off the bus. Other people found they had items pinched.
I definitely recommend Arenal volcano, and the Tabacon hot springs nearby. If you like adventure, rafting in Pacuare River is breathtakingly beautiful. I heard riding the zip lines in the cloud forest are fun too. Avoid the "Highlights tour", and the volcano craters like Iguazu. These are a waste of time.
Surf your brains out in Jaco (spots scattered north and south of there), PuntaArenas and all over the Pacific coast. Warm ocean water. Drink lots of kickass coffee, eat lots of fresh seafood. Learn some Spanish (if you don't already know it) before you go. Ticos are warm, friendly people. You'll see a lot of American and European expatriates, too. Some of the potholes on the roads are the size of swimming pools. Explore the rainforest. And ask Sampson what the "Word of the Day" is.
I think I've got enough to help me pick up a hot tico babe, "Tengo una serpiente grande in mis pantalones" should do the trick
A buddy of mine on these boards is from Costa Rica. His username is Liguista. PM him and I'm sure he will tell you tons of stuff to do. He used to be a tour guide and could probably tell you the tourist traps to avoid and the cool stuff to go to.