There have been several posts on Jaco transportation in the past but I will summarize my own experience with the public bus from Coca Cola terminal. It costs somewhere around $2.50 each way, plus your cab fare to CC terminal of course, which will add up if you go there a day early as well to buy your ticket. If I do it again, and I probably will in November, I plan to find out if there is another way to buy your ticket ahead of time. They are large, very comfortable Mercedes Benz busses with reserved seating. The downside is they are not air conditioned, though that really was not an issue once we were rolling down the road. I do not know if there is an express bus, but mine made several stops along the way, and more on the way back. Surprisingly, the trip still only took about 2 1/2 hours.
If this sounds like a little too much local color, there are more gringo-oriented options. Several companies offer smaller, air conditioned busses for around $20 each way, with pickup and drop off at your hotel. As I mentioned, if you take the public bus, buy your ticket ahead of time to avoid getting shut out. I read that hint but forgot it, and wound up having to sit around the terminal for about 2 hours on a Sunday afternoon waiting for the next bus. Two hours in a bus terminal is no more fun in San Jose than it would be at the Greyhound terminal at 12th and Arch Sts in Philadelphia.
