How do you recommend I go about renting a taxi/shuttle service/van to drive our group on certain days during certain times within CR.

Interbus was recommended to up by friends. We will be using them next month. Check out their website: www.interbusonline.com
Bruce

but they are all scheduled and seem to go only once a day. right?

according to their web site you do have to go by their schedule
Check out Monteverdeinfo.com. They might be able to help you. I have traveled by minivan many times but mostly through a tour company (not a tour just a tour company). I did find one for hire in Flamingo which I used to get to Monteverde after hearing it would take me 2 days to get to Santa Elena from Flamingo by public bus (had to go all the way to San Jose first). You could contact one of the hotels you will be staying in and see if they have any ideas. Costa Ricans are like one long telephone line. Ask one tico and they all know what you want. If you think you will want someone on a regular basis you could try [email protected]. We use him quite frequently and if he can't help he might be able to find someone else.

Costa Rica Expeditions (www.costaricaexpeditions.com) can arrange private van transportation for you. They're good.

More specifically, here's the page on the website for Costa Rica Expeditions:

http://www.costaricaexpeditions.com/....html#TRANSFER

They can transfer between the more popular destinations.

Another note on CRE. We used them many times when we first went to CR. Every time we rode with them they always had two people. One was a driver and the other acted as a guide. CRE's employees are all very knowledgable and a lot of fun. If you are going on a day tour they try to match you up with the kind of guide you would need for that trip.