If you want to proceed directly to Mexico 5 south toward San Felipe [1] from the main border crossing (Route 111), keep right as you approach the border booths.
Stop for the border light, which will flash either green or red. If it’s green, you can continue. If it’s red, you will need to pull over for further inspection. If you need to get a tourist visa or have an FM3 stamped, the immigration office is on the immediate right.
As you cross the border, bear right to get onto Boulevard López Mateos. Continue past the first traffic circle with the statue of Ignacio Allende. Get into the right-hand lane and follow the signs to San Felipe as the road forks to the right and you cross the railroad tracks.
At the next traffic circle, follow the signs to San Felipe, and then take a left at the next light. This road will turn into Mexico 5 and will take you all the way into San Felipe.
Coming from the new border crossing to the east, the road will end in a T a few hundred meters from the border. Go right at the T and then take a left onto Boulevard Gomez Morin. This will take you straight to Mexico 5. Stay in the middle of the three lanes to avoid most of the abrupt stops.
The drive is mostly flat, but you’ll have plenty to look at as you go from farmland to lakebed to desert. About an hour and a half into the drive you can often see the Gulf of California in the distance. As you get closer to San Felipe, you’ll encounter construction crews that are widening the road from two lanes to four. Eventually, the entire stretch from Mexicali [2] to San Felipe [1] will have four lanes.
The total drive time from the border to San Felipe is around two hours. For the return trip north, add at least one hour to make sure you have enough time to cross the border. During rush hour or on holidays the border wait can be several hours.
Links:
[1] http://www.moon.com/destinations/baja-cabo/mexicali-san-felipe/san-felipe
[2] http://www.moon.com/destinations/baja-cabo/mexicali-san-felipe/mexicali