This depends a great deal upon where you are. Some places, gobblers will gobble like crazy in the evening,...and in some, you couldn't get them to gobble if your life depended upon it.
Assuming you are in a place where they will gobble in the evening, pitch black dark is generally not the time to try to get them to. The time period they will most likely gobble is when daylight is fading into darkness. From my experience, prime time for roost gobbling in the evening is starting about 15 minutes after sundown and lasting for about twenty minutes after that.
If your two locations are close enough to drive quickly between the two,...and assuming your birds are inclined to evening roost gobbling,...you could, in theory, start at the first location and then move to the other and successfully locate gobbling birds.
Morning roost gobbling is much more reliable. Often gobblers will sound off in the morning when they would not make a peep in the evening. If you can go out in the morning rather than the evening, that is almost invariably a better choice for locating birds on the roost.