Re: Please Help what is this worth
For Florida, you can find guides that specialize in fly fishing for those species, especially tarpon. They would have top notch gear that you could use on the boat- just be sure to mention this when you book the trip. They should provide this at no extra charge with the charter. If possible have them bring both a 10 weight and a 12 weight.
Costa Rica might be a different story, with limited (if any) fly gear available at some lodges- but again you could confirm this when you book and get specific recommendations for gear based on both the size/species you will be targeting and all the other stuff you'll have a reasonable chance of running into. Many lodges in Costa Rica have mixed bag type fishing with opportunities for tarpon (often blind casting in lagoons as opposed to sight fishing on flats, which would be more typical of fishing in the keys), snook, permit, roosters and various off shore species including mahi, sails, and small tunas etc. Many folks would bring an arsenal of outfits with different line weights for this type of fishing, but for versatility, you might consider a 9' 10 weight for a mixed bag of inshore and offshore fish. (if you were concentrating on blue water off shore species with a reasonable chance or running into marlin and large tuna, and/or large tarpon 100lb+ specifically, a 12 weight would be probably the way to go.)
There's usually a big difference between a 10 and a 12 weight in most rod line ups (same brands/models just different weights), with the 10 having a much more caster friendly action, and the 12's (and 11's) being quite a bit stiffer-- with a 10 weight being more similar in action to an 8 weight than a 12 weight is similar to a 10 weight. Typically 12 weights and up are used for specific shots at spotted fish as opposed to blind casting all day-- that would be very tough. A 10 can be used for sight fishing as well of course, but also blind casting in deeper water-- which can add up to a lot of repeated casts over a long day on the water. For most folks, casting a 10 weight is a lot easier, and the first goal has to be getting a fly in front of a fish.
And some of it will come down to your experience and the stuff you may have already or plan to get down the road. If for example you already had an 8 weight for inshore SW, and a 10 weight for heavy inshore and small medium off shore, than a 12 weight would be the next logical addition and you'd be covered for pretty much everything except huge marlin and tuna.
Big, strong, fast fish like these can be tough on gear. High end rods and reels can run 600-700 a pop each for new ones at retail pricing. If you're on a budget you might look at some options for rods like TFO (around 250 new, 150-175 used for Axiom, TiCR, TiCrX models), Sage RPLX or RPLXi series (around 300-350 used), and a used reel like a Pate Tarpon (about 550 new but 350 ish used, built like a tank). I'm sure there are many others out there too that would be good choices but those would be some of the ones I'd look at.
If you have other buddies that fly fish, a local FF club, or local fly shop it would be great to get some casting in with some of these different outfits and line weights to get a feel for throwing with them.