Hi Mike,
Just head in on the main road. The fields on your left usually have abundant geese.
You can also walk to the lake along the trail that's accessible from the first parking lot on your left.
I think you'll have success most any time of the day.
The Visitor Center just up the road, on the right, is worth going into, for refuge maps, etc.
Enjoy!
I went there a couple of times in the last days. The birds are in different spots every day but it's hard to miss them. Just go up and down the road and if they are not there, they might be along the tour route at stop 3. Both mornings and evenings can be good. I prefer days with high clouds to prevent harsh shadows.