Going out with a guide on a float trip doesn't always guarantee results. That's just fishing. Often these trips are booked in advance as they stay pretty busy all season. This means sometimes the conditions can be an obstacle (high water, poor weather, etc.).
On one trip, the river was super low and crystal clear and we fished all day under bright skies. Not always ideal but we caught fish, and they were scattered and mostly on the smaller size.
The other trip was in the Fall, one of those crap days when a front moved in, right in the middle of two steady weather patterns we were experiencing. We had high winds and cool temps all day and fishing was tough. We rebounded in the last hour of the float, when the front passed, the wind calmed down and the temps actually rose even though the sun was getting ready to hide.
What you do get is a great day out on the water with guides that will share their experiences fishing the river as well as showing you water you may have never seen. I always learn something new on every trip.