At Merced, I've found the cranes easiest to photograph literally right at sunrise and sunset, and they can be frustrating by choosing ponds that aren't very close. But sometimes they're 100' away.
The other place to get intimate with cranes is at and around Cosumnes Preserve, a couple of hours north, though the numbers are hundreds, not thousands. You can often find large numbers feeding the fields around Woodbridge and Staten Island as well, or hanging out in the ponds along Desmond Rd. or the main preserve, though not always very close.
Ducks and geese in general at all the refuges don't seem to mind people a lot, and the Black Crowned Night Herons are positively ridiculous - you can sometimes get to 20'. There's a heron roost or rookery (never seen nests there, but a hundred or so herons at a time) at Colusa. Raptors - hawks, falcons, and a few eagles - at all the preserves, as well as scarcities like shrikes, bitterns, and the unbiquitous great horned owls.
I love cranes, but biggest challenge I've found with sandhill cranes is that they really don't come in the evening until the light is just about gone, and finding them in the morning dark means driving around with your windows open hoping you hear them.
I've heard that the drought has made this not a great year at Klamath, though perhaps this last series of storms will help.
I made it to Bosque once for a few days when I was working in Albuquerque, but but wasn't a good year or good time of year. There was almost no water, and I definitely found the numbers of my fellow photographers a bit off-putting. Maybe I should try again...