Same day tickets to Santa Teresa from San Jose?

Hey guys.

Thanks for all of the good info I've gotten so far about Costa Rica travel in thumbing through these threads. It's been so helpful in planning. Now my trip is just a few days away and I've got one last concern.

My flight is arriving to San Jose in the evening on Saturday, the 21. We'd really like to take the 6 am bus from Coca Cola the next day (Sunday), but have heard that sometimes it's impossible to buy tickets for your bus less than a day in advance. Does anyone know if this is the case for this route? If so, can anyone recommend a shuttle company that's reliable and will take last minute reservations? We'd really like to get out of the city as soon as possible!

Advice is much appreciated. Thanks again!!