We have driven San Diego to Rocky Point many many times. I've found the best route to be going through Tecate and taking the toll road. You by-pass Mexicali and the congestion there and the posted speed is 110 km/hr. The road to Tecate and the switchbacks at La Rumorosa are hairy and car-sickness is a factor. Therefore, we mainly cross at Calexico East. No incoming inspection, 3 left turns and you are on the highway. We make it from North San Diego County to Rocky Point in 5-1/2 hours. Have also taken the Hwy 5/4/3 route and it is quicker and less miles. You do go through many small towns, the roads are in so-so shape and you have to be aware of farm equipment and animals. Crossing at San Luis will add about 45 minutes to the trip.