It's a typical (if fast-moving) cutthroat stream above the falls. Below them there are other fish including bulls, whitefish and anything else that swims up out of Abraham Lake. Super-beautiful scenery out there. Crescent Falls are worth seeing; the river pours into a deep gorge right below Crescent Falls PRA.
I've found presentation more important than specific flies - the crazy cross currents and speed of the river make a drag-free presentation tricky and short-lived. I've also found it pretty cloudy with glacier silt, so it's hard to sight fish, but the fish are where you think they should be and will wait patiently for you to make the perfect cast, even if it's your 75th cast to the same pocket.
I've had success with the (well, my) usual cutthroat flies: #6 Yellow Foam Stimulator, #14 H&L Variant, #18 Parachute Adams, #14 Copper John, #12GRHE, etc.
To park at the campground/day use site, you need to ford a small stream. I've done it successfully in a 2WD Jeep Compass, so it's not like you need a jacked-up 4x4, but I wouldn't try it in a low-clearance car or with a huge trailer (there's a homemade sign saying a 26' trailer bottoms out). If you come in a Civic towing a 28' trailer or something, there is another parking lot before the creek, it's just not equipped with picnic tables, outhouses or campsites.
If your wife (or whoever) doesn't want to fish but still comes with you, the flood this year created quite a nice sandy beach right near the campround.