If you're looking for a meeting place or a good stop around ½ or halfway between Guilford and Hartford, you can try East Wallingford, CT, which is about half an hour northwest of Guilford, or about half an hour south of Hartford.
About ¼ or a fourth of the way, you can stop at New Haven, CT. This is about 12 minutes west of Guilford.
About ⅓ or a third of the way, you can stop at Hamden, CT. This is about 18 minutes northwest of Guilford.
About ⅔ or two thirds of the way, you can stop at Highland Estates, CT. This is about half an hour north of Guilford, or about 16 minutes south of Hartford.
About ¾ or three fourths of the way, you can stop at East Berlin, CT. This is about half an hour north of Guilford, or about 14 minutes south of Hartford.
If you drive straight through without stopping at all, the total distance is 52 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 51 minutes.