We snorkeled with 6-8 over two days off Utila. The EcoOcean folks and others have Whale Shark research facilities in town so I'd disagree with the above poster. It is however very seasonal - on our trip, we had an expert from Shark.org doing research so we participated in a cell sampling and some photography that resulted in my buddy submitting photos of what we thought was a new one - later they found it in the database.
If you find Bonaire inexpensive - wait till you see Utila town prices...surprising since it's so remote. Lots of backpackers end up there for some odd reason. You will have a 2nd flight from the mainland or Roatan - that runs about $150 r/t. Or there's the ferries from Roatan - $100 r/t but that will kill a morning/afternoon. We were on Roatan at noon, Utila at 5PM.
Some of the shops run special trips just for that - on ours we did two dives in the morning then looked for them nearby. If we found them, we dropped on them, otherwise we called it after an hour or so and did a third dive instead. The odds of diving with one are pretty miniscule, they like the deeper water off the north side and you won't be diving at those depths.
Idk if it's always the case but most of ours were 16-20' juvenile males. One big female once - longer than the 30' boat we were on. She was barely moving her tail and it was all we could do to keep up with her.
The legal number of drops per boat is limited so the captains cooperate via VHF to improve their sightings/tips for all.
Honduran regulations are snorkel only, boat stopped and only two drops per boat with no more than 12? snorkelers in the water simultaneously. I saw the last rule broken several times.