We went around 10:00am, because when we called to make a reservation the owner told us there was rain in the forecast and he wanted to get us in before that happened. After we arrived, it took about 15 minutes or so for the hummingbirds to come out and start feeding from our little bottles. The guide said it takes a little while for the birds to get used to you, but once they are comfortable they will be all over the place.
This worked out perfectly, as we hit Just Natural afterwards for lunch.