Well, here is how I see it for our family of 5:
Airfare (SAN - SJD): $500 * 5 = $2500
Airport Transfer (round trip): $175 or Car rental for week: $800 (conservative for minivan). Just got this quote from Budget Car Rental and grayline.com for the airport transfer.
Total for flying: $2675 or $3300
or
Gas for 2000 miles round trip at $2.70/gal and 20 mpg: $270
Auto Insurance & tourist card: $200
Hotel 2 nights (1 each way): $200
Total for driving: < $700

I know I'm not taking into account the wear&tear on the car and physical fatigue but it means saving more than $2000. I've driven for 8 hours continuously with no problems before. If you think Budget is ripping me off for the minivan rental, can you suggest a different rental car agency where you got one for a week for $100?

Which GSM cell phone carrier did your husband use? How many years ago was that? Did he purchase that in Tijuana?

Is it possible to get a Tourist Card before entering Mexico? How many days in advance?
Thanks everyone!