It's actually about 20 minutes from downtown San Diego depending on traffic. What you're not accounting for is the 2+ hours waiting at the border to come back. 

People are just completely irrational about gas prices. You save $2 per gallon, so that’s what, like $20? Or $30 if you have a big car and your tank is almost completely empty? And according to Google Maps, Tijuana is 20 miles and 40 min away from San Diego, or 40 miles and 80 min round-trip. So you use 1.5 gallons on…

He’s pretty clearly a sociopath to me as an armchair, completely uneducated psychologist.