El Mazateño in TJ...YUM
Without a doubt, one of the finest shrimp tacos anywhere. And the octopus ain't bad either
You should be crossing at Otay anyway... northbound anyway. From San Ysidro it's not so hard, just hard to explain.
After you cross, stay toward the left and follow signs for Paseo de los Héroes. Just drive slowly, nobody expects you to jackrabbit out of the inspection area. You'll know you've successfully found Paseo de los Héroes when you pass the Costco.
Take a "left" at the second traffic circle (meaning the third exit) onto Hwy 1 free (signs will point you to "Aeropuerto").
At the third traffic light, you'll turn right onto Defensores de Baja California. You'll be following signs for TEC-UABC (the technological university and the Autonomous University of Baja California). You'll go up a small hill and then an absolutely enormous hill (trust me, you can't possibly miss it). Just before the third hill, the pavement changes colour and the main street turns left. There's a vidriería (glass shop) on the corner. Turn left with the main road onto Soledad Orozco. Go one block and turn right, still following the really obvious main road, to 3rd St. There's a Modelorama on the left side where you need to turn right. Go two blocks and turn left, still following the obvious main road, onto Guadalupe Ramírez. Go two blocks and the road will turn very obviously right. Go through the traffic light and park.
You can Google Street View the entire journey if you like.
From Otay it's much easier: cross the border, turn right at the second major street (Fed. Hwy. 2, signs toward the airport). Then just keep going, following signs for UABC-Calz. Tecnológico. You'll go about 3 miles, passing both UABC and TJ Tech, and it'll be on your left, just before the road makes a sharp turn left and downhill.