If you’re near San Diego, why don’t you just take the trolley down to the border and cross at San Ysidro? Take your passport, other forms of ID if you have that and plenty of money. That way you won’t have to worry about driving here or there without a license.
Crossing by foot at San Ysidro is a good idea. There are bus terminals within walking distance. I don’t trust the cab drivers. A lot of the cabs don’t have seat belts in the back seat. I would not recommend going down there unless you have a Sentri pass. Without a Sentri pass the pedestrian line for entry back into the United States can take more than two hours.