Anna Maria island should be great in April. We've had a warm winter and some of the fish are already coming out of their winter haunts.
Best all around rod for inshore saltwater is an 8wt. If you have one, bring it. You can go as low as a 6wt, but you will have trouble with wind.
There is some good fishing water on both sides of Anna Maria Island. It may be warm enough to fish off the beach, but you will need to do it very early in the morning before the beach people come out. There are also good flats on the back side of the island between the two fishing piers.
Bring some hightop basketball shoes or wading shoes to protect your feet. I doubt if you would need waders that time of year. I would bring a stripping basket if you have one, or make a cheap one if you don't.
My favorite flies are chartrues and white clousers and decievers off the beach. I also like bonita bunnies (big zonkers). For the flats, I like bendbacks (particularly the prince of tides) and kwans.
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