At one time or another I've found dry bypasses in Phantom Canyon for all the deep pools that you can't just wade through. Of course when there's been heavy spring & monsoon season there are lots of changes in the depth of the pools and the boulder configuration in and around them so YMMV.

From the bottom the first barrier that stops most people is the water chute that looks like you have to swim through and then climb it; but you can make your way around to the left. Don't climb too high; go upstream and back towards the creek as soon as you can. Towards the end you're on very smooth slippery rock sloping sharply down to the creek just above the chute; either control-slide down into it and get your feet wet or cling on like a fly and make your way across the last 20-30 yards to dry footing.

Quite aways further after an easy bypass or two, there's a real overlander to the left, long and rough climbing high; maybe not worth it. Then three/four fairly straightforward ones. Finally about 1/4 mile below the barrier falls there's the standard long bypass on the right up to basically the Cattle Route and then down near the top of the Falls; cairned from the top down. Alternatively, sometimes people will leave a rigged climbing rope at the Falls though the Rangers take them down as soon as they patrol. I don't have the upper body strength to do a straight climb up the face but if it's long enough to swing over to the right there's a crack that is a pretty easy short climb with the rope for confidence and substituting for a couple of missing holds.

The water in BA Creek may be too high/swift to cross in April. With rope and technique you can ALWAYS get across but it may not be fun. Check that out from the bottom before you do your trip down Phantom Creek and find yourself stranded on the other side. Frankly the Lower Creek isn't all that pleasant until June not just because the water itself is very cold but the frequent narrows get little sun. It's chilly, particularly if you've gotten wet and there's wind howling through the slots.

You may find water in the lower area of the Flats maybe 1/4-/1/2 mile up from the Alley, in the drainage you have wanted to get out of for easier walking. Either stay in the drainage or keep looking down over the edge at the likely pooling spots. Having a water resupply there can really change the nature of a hike as you can wander around for miles and have water to get back to, and though the sun may be bright the temps are usually such in April that it's not oppressive being out in the open like that. In late May & on you'd fry.

In any case, enjoy!