If you're renting a car, just make sure to have a transponder on it for toll roads; a couple years ago, this was automatic with Hertz. Taking expressways along the coast can save a lot of time, and they're generally pleasant roads with rest stops and some pretty views. On the expressway, it's a fairly short drive to the Spanish border or to the west-facing Atlantic coast, but it can be slow and frustrating on other roads, even in shoulder season.