I have been on Truth Aquatics sister boats, Vision and Conception, many times (12 or more, stopped counting) but never in April. Basically the terrain and sites vary depending on where the captain can get to with the boat (this is completely up to the weather and wind gods). I have really enjoyed the diving, lots of nudis, kelp bass, kelp, stars, scallops, sea lions, etc. etc. Not too different than Monterey/Carmel diving except that you can count on the water being just slightly warmer (about 10 degrees) bring a good wetsuit and/or dry suit, 5 dives a day or more always make me cold. The vis depends on how much the water has been stired up by storms. I think you will like the boats, I sure do. The bunks are cramped, I always bring my own sleeping bag, light blanket, large and small towel and pillow. I try to get one in the middle of the boat, if the seas get rough you will be affected by the seas much less at the center of the fulcrum. The food is good and plentiful but basic. I always bring a couple bottles of wine for the nights there is no night dive (highly recommend the night dive- easy to just stay dry an warm on the boat but well worth the effort usually). Some guys bring a cooler of beer, cigars, whiskey or what ever they enjoy at the end of a long dive day. The boats move around alot trying to get you the diving conditions you are looking for. If you were unhappy with the dive site, let he captain and crew know in a nice way that you would like to move to try something else. Don't let them just park the boat and keep an open gate where you don't want to dive.
I would echo the advise to bring a big plastic tub for your bc, flashlight, gear etc. which you can put in the center above the tanks. It helps to get to the dock early so you can have a good choise of where to put your tank and gear, not a big deal though I have held the boat up being the very last one on and had to store my gear along the side toward the bow and it did not detract from my experience.
My #1 recommendation though would be to bring your own coffee cup. I bring a stainless steel insulated cup with a screw on top. They provide plastic coffee cups which you are supposed to write your name of the bottom but they all look the same and make any beverage in them taste like diesel fuel. Trust me on this, you will be the envy of everyone on the boat if you bring an insulated cup.
Most of all relax, enjoy, protect the marine eviroment, and be safe.
Ron