If you're looking for a meeting place or a good stop around ½ or halfway between Coronado and Phoenix, you can try Yuma, AZ, which is about 2½ hours east of Coronado, or about 3 hours west of Phoenix.
Another possible place to stop near the midpoint is Fortuna Foothills.
About ¼ or a fourth of the way, you can stop at Mortero Palms, CA. This is about 1 hour east of Coronado.
About ⅓ or a third of the way, you can stop at Mexicali, Mexico. This is almost 2 hours east of Coronado.
About ⅔ or two thirds of the way, you can stop at Tyson, AZ. This is about 3½ hours east of Coronado, or about 2 hours southwest of Phoenix.
About ¾ or three fourths of the way, you can stop at Sentinel, AZ. This is about 4 hours east of Coronado, or about 1½ hours southwest of Phoenix.
If you drive straight through without stopping at all, the total distance is 358 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 5 hours, 23 minutes.