The power rangers are in and out REALLY quick and don't show up all that often. The first time we got two, and we happened to be over there the second time and got three. They go to the same spots each time. The black ranger is to the far upper right (and has a fairly short line each time), the pink ranger is just a little over to his left (and a very short line, almost all girls), the green ranger is at the end of the right sidewalk (long lines), the red ranger at the end of the left sidewalk (long lines), and the blue ranger is up to the far left (again long lines).
As soon as they get off the car, you can get in line for them. You do not need to wait for all of them to get off. My DH grabbed DS4 and got in the line that meant the most, then I'd go get in the other line with DS15months. When DS4 finished (by design he'd finish first), they would come replace me in line (even swap, one adult, one child--CMs support this when you aren't adding an extra 15 kids), and I'd go get in another line.
The first time we were there, my son was next with the red ranger when they were cut off. The second time one minute to cut off time (they do give you warnings at 5 minutes out--they're out for a total of about 10 minutes), he was in line for the pink ranger and they stopped doing autographs and just pictures to accomadate more kids. The pictures with all the Power Rangers are WONDERFUL! They poise the kids.