Almost all the excursions for adventure stuff is going to be cheaper out of Jaco as it is all so close unlike going out of San Jose. In Jaco, I recommend to my clients the Jose's Crocodile Tour (
http://crocodilerivertour.com/), ATV tour (with good advice from Brooklynkid above (
http://axrjaco.net/)), zip lines (
http://www.canopyvistalossuenos.com/) and a day trip to Manuel Antonio as the top 4. If you like hiking, Manuel Antonio is a MUST. They have recently put in a ton of boardwalks that make the trekking much easier than when they were sand or gravel and there are miles of neat trails to explore. If you want a boat cruise, try the water taxi between Jaco and Montezuma...a neat counter culture town with a nice beach and waterfalls.
Golf in Jaco is at Los Suenos while in San Jose, there are several courses but I like Valle del Sol.
http://www.golflaiguana.com/http://www.vallesol.com/eng/golf.htmlOut of San Jose, the best tour is probably to the two volcanoes, Poas and Irazu. Poas has a huge crater and is still active...you will smell the sulfur. There is also a good hike over to a neat crater lake. Many tours will also include La Paz waterfall gardens (
http://www.waterfallgardens.com/index.php). Irazu is the highest volcano in CR at over 11k feet with a view of both oceans on a clear day. Maybe the best thing about Irazu is next door Turrialba. If you get lucky, you might see it REALLY erupt. Has been doing it every few weeks for the last few months. These are all videos shot from Irazu.
https://www.youtube.com/watch?v=z4DbaX_NUDohttps://www.youtube.com/watch?v=fDXewVDvrkwhttps://www.youtube.com/watch?v=uGOd-UmQoPM