Christianitos Rd at I-5 in San Clemente is on the OC border, so here you go for the Camp Pendleton route. Google Maps suggests the I-5 shoulder because it is permitted (on an off depending upon what seems like endless freeway construction) but hardly pleasant.

Riding through CP now requires applying for a permit, as well as a US Government issued ID to enter.

Riding through the base is nicer than the freeway. Pre-register, bring ID and wear a helmet.

When you leave Oceanside Harbor, cross underneath I5 then be careful - you have to cross 2 lanes that are the offramp lanes to the base from North I5. Once you're on the base, pass the hospital and shopping center and make a left at the 3rd light (1 mile past the gate) and go up a hill to Stuart Mesa.

Follow this road for about 6-7 miles until it ends at a stop sign. Make a left, go up a little hill and you'll see the Las Pulgas gate.

Exit the base and as soon as you go under the railroad tracks, turn right into a small parking lot and go through it. Go through the opening in the fence and continue. Straight 1/2 mile then veer left with the road and enter the tunnel. When you exit, turn right and follow the path until you come to another fence. Go through the opening and you'll be in a parking lot for the San Onofre campground. There are bathrooms and picnic tables if you want to rest. If you go to a bathroom and it's locked, try the next one; sometimes they only open some of them.

If you continue, you'll exit the campground and be on the frontage road in front of the power plant. Keep going, down a dip then up a little hill, maybe 1/2 to 1 mile. At the top of the hill, look to your left across the street and you'll see an opening in the fence. go through this opening and turn right. Follow this path another mile or so and you'll end up at a street in San Clemente. If you go right, cross the freeway and there's a Carl's Jr.

If you read this and wonder about going through openings in the fence, don't. This is the route that thousands of cyclists use. Also, my distances are approximate. I don't have a computer.

Just dropping in an alternative way of getting to Camp P's gate from Oceanside Harbor without crossing the I-5 ramps.

When you enter the harbor from the south on Harbor Dr, and come around the left hand bend, there is a narrow tunnel on the right side of the road - just before Joe's Crab Shack. Turn right into the tunnel, and you'll come out on a big hotel parking lot. Go thru it onto San Luis Rey Dr and then take a right at Monterey Dr. When you get to the Coast Hwy, hop onto the southbound sidewalk. You'll see a ramp going under on the right side of the sidewalk. It's a pedestrian underpass. I'm afraid it's a bit dark down there, smells bad (homeless folks hang there at night), and often has broken glass and other trash.... but it has no car. :o) You'll have to hike-a-bike up a set of concrete steps on the other side when you pop up on San Luis Rey Dr cul-de-sac. Take the first left (San Rafael Dr), and it will drop you off onto Vandergrift Blvd just in front of Camp P's gate.

It's sort of round-about way, and there's the steps to hike the bike up... but I still quite prefer it to the Russian roulette that crossing the I-5 on/off ramps feels like every time!