Somehow every time I've made this drive I've screwed up and ended up driving at night...and yet somehow it was still stunning. Not a ton of diversity in it (not like you'll be going through lots of towns or residential areas), but it's still gorgeous.
Our car got stuck when we rode it, stopping for a driver who decided to run a red light. Can't stop those cars suddenly or else they lock up. We had to walk the rest of the way, fortunately it was on the way down to the Wharf.
As everyone else says, best zoo around. But more than that, the surrounding museums and Balboa Park are awesome too. I suggest getting a re-entry stamp and go back and forth as much as you like.
This is a must for zoo fans. Don't skimp on time for your visit; there's a lot to see here. Better yet, plan several days so you can check out the zoo's sister properties.