Jared, When I was in Naples a couple of years ago I had some luck very early in the mornings on the town beaches. Once the bathers show up things pretty much shut off, but I was able to get in a couple of hours of sight fishing for jacks and misc other fish. Fly choice didn't seem to matter much as long as it was white. While I was there I saw a med sized tarpon(~75lbs?) caught by one of the bait fishermen off the naples town pier, so they are out there...
Have your brother in law get in touch with The Everglades Angler
in Naples, they were very helpful for me and if he's considering a guide they work with a number of good guides as well.