Angryuser, that looks really nice. What is the spider situation down there? I've never gotten a straight answer from anyone.
I don't recall any issues with spiders, but they don't freak me out, so unless I wake up with one crawling across my face, it's not going to stand out 12 years later. And that did not happen. 
Costa Rica does have more (types of) bugs, in general, than about anywhere else on the planet. The biodiversity is at the top of the charts. We spent time at a biological research station in the jungle, and one in a cloud forest on a mountain doing experiments (Biology and International Affairs classes). We saw a *lot* of bugs. Along with monkeys and birds and sloths and all kinds of stuff.
I have a buddy who picked up a frog down there he shouldn't have (in general, I think most people avoid touching extremely brightly colored reptiles unless given the go-ahead to do so from a handler). Never saw any weird spiders.
Mr. Man I second what angryuser said about getting out of San Jose ASAP. And I also loved Manuel Antonio (La Posada was cheap and cool
http://www.laposadajungle.com/). We didn't really go anywhere else.
I'll add that, if the car thing sketches you out, it's really cheap, fun and fast to catch a Sansa flight to Quepos or some other places and then cab it from there.
Finally, one small detail that nobody ever mentions- coming back, you have to pay a small ($25?) per person tax at the airport before they let you board a plane to leave the country. And I'm pretty sure it has to be cash.
Enjoy!