I usually think bonefish in April, but that doesn't quite sound like what you're looking for. I've fished SW Fl my whole life, April can be a hit or miss month for tarpon, May, June, July are a little more solid, and for redfish, I like Aug and Sept. Although, April is a really good snook month. Mid April can also be a little early for tarpon in the keys.
I think you might like Mexico in mid April. You have a lot of options, you could fish the flats south of Cancun, you could fish from an island called Holbox for giant tarpon (big schools), or you could try Cabo for surf fishing and offshore. April is a prime month for a wide range of fishing there. The cost for fishing those places also isn't too crazy.
