http://www.rainforestadventure.com/cost ... xcursions/ is a resource I've seldom seen listed on CRT.
This experience is "...just around the corner....." from San Jose in that is very doable in just a couple of hours there and back; longer if you sign up for the full monty. You can use one of their transports to get there (addtl. costs), or take a bus ("public") right to the front gates of this private nature preserve.
Actually my first Tico bus ride was to this place. The booking office will tell you how to get to the bus station as it's just blocks from the booking office. Where's the booking office? Most guys have walked right past it: It's, essentially, across the street from where Harry's Bar is (Avenida 7, Calle 3 y 5); on the same side of the street as Hotel Santo Tomas and pretty much next to that hotel. While going directly to the office to book your tour, check out the "hidden" massage parlor, Musas (name changes all the time), which is on the same side of the street as the bar.....just further down the block a bit. Musas is most affordable, but it's hit or miss. There are diamonds in the rough in that place if you're there at "the right time".
You'll see this office I'm referring to. If you prefer, go through your hotel front desk and those guys will get a commission.....the cost of entrance and such does not change for you. If you choose to take the public bus, you'll find this simple ride exposes the new bus rider/member to riding the bus throughout Costa Rica and seeing sights not typically seen. The bus ride to the park, alone, was worth the price of admission.....took less than 45mins as I recall. If you take that bus, just be certain to secure everything as pick pockets abound. The bus stops right in front of the park (tell the driver you want to stop there); and the public bus will pick you up to get back to the bus station from where you began in San Jose. You do need to "flag down" the bus on the way back.