I made this drive 2 Saturdays ago. We arrived at the airport 1 pm, but after all the customs and car rental time wasted, we drove off at 3:30 pm. it gets dark by 5:30.
We survived the "Mountain of Death" but I would never do it again. narrow winding road in the dark, with dense fog, rain, over aggressive drivers, and cliff drop offs that can easily kill. Don't do it !
We should have driven to Jaco and stayed there because its easier to find your way out of San Jose to Jaco than to try to wind our way thru San Jose to get to the Pan Am Hwy on the far side of town from the airport. Its 2 hrs from airport to Jaco, then next morning 2 more hours from Jaco to Dominical. There is a Best Western in Jaco that is large and easy to find and right on the beach. Better than the Best Westerns here. You might make it there for the sunset which is spectacular.
1 hour of the 2 hour drive the next morning to Dominical will be on an unpaved bonecrushing dirt road with lots of bridge work underway. Still beats the heck out of Death Mountain.