All of the locations you mentioned, Jupiter/WPB/Lauderdale/Keys, are all great locations for diving and you won't be disappointed with any that you choose.
If you want a guaranty of seeing sharks, Jupiter would be your best bet in my opinion. I dive with Jupiter Dive Center frequently and highly recommend them: there's a couple other operators in the area too and Scuba Work's boat gets high marks on SB though I've never personally been on it.
WPB diving is also very nice, less of a guaranty of seeing sharks, but you stand a fairly good chance. The reefs in WPB like the Breakers, always seem a bit more colorful to me than Jupiter, probably because they are shallower and the sun illuminates them better. Ops I've used are Jim Abernathy, Scuba Club, Walkers, Narcosis, but there are a lot of others in WPB.
If you want pretty tropical reefs that are protected so are not fished and have significant fish life, the upper Keys would be your best bet. However, the Keys also has some pretty cool wrecks like the Spiegle Grove, the Eagle and the Duane, though I'm not sure those would be appropriate given your profile indicates less than 25 dives. Good boats are Conch Republic and Silent World. There are not very many operators that go to spearfishing areas in the Keys that I know of: a lot of the sites are in protected areas so you'd need to clarify the dive locations with a dive operator before you book.
I think the Pompano/Lauderdale area is one of the overlooked gems of diving in Florida; locals know its good but visitors miss out. The shallow reef line is one of the most beautiful you can find: I love the gentle drifting on the Coppenhaggen site (or the drop off or the nursery sites). However, the area also has a ton of wrecks some of which are shallower than the ones in the Keys. The Lauderdale wrecks are also smaller in size but still pretty neat; the Ancient Mariner, Aqua Zoo, United Caribbean are examples of some of the shallower ones. I've used South Florida Dive HQ, Scubatyme and Pompano Dive Center.
If you really only have 25 or fewer dives, keep in mind that spearfishing is one of those activities in which you can get task overloaded pretty easily if you're not experienced: especially if you have a bunch of sharks circling you and bumping you to get to your bleeding fish (which you'll get in Jupiter and parts of WPB if spearing). Its unlikely that you'll be using a full size spear gun on Lionfish, they usually run to small crevices and most people use undersized pole spears or 'lion fish tamers' to kill them. Lastly, its not a bad idea to get Nitrox certified when diving in Jupiter, WPB or NC for that matter. On air, you won't have much bottom time.
Have fun on your trip: all south Florida diving is fantastic.
