If you're driving yourself, you should always try to be at your destination by dark. That's 5:30-ish year round, give or take 15 minutes or so. It is 5:25 p.m. here right this moment and it's going to get dark very soon. It's one thing if you're in Manuel Antonio, say, and you're driving somewhere there in the evening for dinner, but to be driving after dark is not good idea for a visitor who doesn't know the roads.