We just returned from our first time to Nosara and it was an awesome trip, but we had a bit of an adventure driving there from San Jose that I thought I would share with my fellow travellers in hopes you will avoid our follies :)
We were a group of four couples and rented two Suziki Grand Vitara SUVs from Service Car Rental. Aside from the fact that they were an hour and half late meeting us with the rental cars, everything was fine. The cars were great, everything cost what they said it would in the quote, friendly service. We got the GPS and unfortunately got on the road later than we had hoped.
We departed the San Jose Area around 2 pm and were about an hour from Nosara at 7 pm when the GPS told us to make a left onto a dirt road. We had read a bit about this drive and assumed this was the "dirt road". Boy were we wrong! Apparently it is the dry season road. At first we thought it was awesome offroading in Costa Rica, until we got one of the SUVs stuck in about two feet of mud/water. Fortunately the exhaust and engine were not underwater, but try as we might, we could not push the car out. We had no rope to try and pull it out so we drove one car back out to the road we had turned off of and waited. Lucky for us, who should drive by, but an expat named Michael with his wife and a beast of an '86 Dodge Raider (and a tow rope). He happily pulled us out of there and about an hour later, we were back on our way. THANKS MICHAEL!
We were extremely fortunate, but wanted to share with anybody else travelling there for the first time to be careful about blindly following the GPS. Also, due to our late start, it was pitch black at this time, so make sure you get an early start from San Jose.
PS - Nosara is amazing. We stayed in Playa Guiones, just up the road from Harbor Reef, and it was wonderful.