Mixxalot, a possible solution to your date in Del Mar is FlexCar. I have not yet tried this, but they have cars that can be rented by the hour, scattered around town. According to their website there are about 80 of these cars in San Diego, they are concentrated south of the 8 and north of the 94 and west of the 15. There are 29 of them downtown, from pickup trucks to mini coopers, to 2-seat convertibles (that should work well in Del Mar). There are several in Hillcrest and the beach areas as well.
There is a $35 annual membership fee, then it starts at $7 per hour, or cheaper if you pay for a monthly plan.