SD has lots of stuff. The area by the zoo is huge. Large park and other scenic stuff. There's sea world down there too. Gas lamp district is a nice place to visit at night.
Agree'd with FBP that 101 is a much more scenic drive. You can stop in Pismo or Santa Barabra on the way down. While there you can hit up solvang if you're into wine. It's a good midway point. And if you're driving down to SD you have options to take a break in LA too since you'll be passing through it.
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1965 Fastback Mustang (black) : 1999 MR Si (Vortech Fed)
1971 Orange Honda Z-Coupe (600cc of pure power) : 2005 YZF-R6
