If you're looking for a meeting place or a good stop around ½ or halfway between Carlsbad and Dana Point, you can try Agra, CA, which is about 17 minutes northwest of Carlsbad, or about 17 minutes southeast of Dana Point.
About ¼ or a fourth of the way, you can stop at Yaldora, CA. This is about 8 minutes northwest of Carlsbad.
About ⅓ or a third of the way, you can stop at Stuart, CA. This is about 11 minutes northwest of Carlsbad.
About ⅔ or two thirds of the way, you can stop at San Onofre, CA. This is about half an hour northwest of Carlsbad, or about 13 minutes southeast of Dana Point.
About ¾ or three fourths of the way, you can stop at San Clemente, CA. This is about half an hour northwest of Carlsbad, or about 8 minutes southeast of Dana Point.
If you drive straight through without stopping at all, the total distance is 31 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 34 minutes.