The most famous scenic drive near San Diego is the city's own 59-mile route, which tours all the area's famous neighborhoods and attractions. It's a great half-day introduction to the scenery and history of San Diego. Another great drive is Route 75, which from Coronado along the narrow spit of sand which connects it to the mainland, known as the Silver Strand, and is a unique drive with ocean on both sides.
Ranging farther afield, Interstate 5 heads north towards Los Angeles along a scenic route hugging the coastline, and a short ways east is the Sunrise National Scenic Byway, a mountain drive with stunning views of the Anza-Borrego desert thousands of feet below.