April is about the best time next year. A third option to consider:
Deep Blue Utila - swim with whale sharks at our all inclusive resort.
We were there a couple of years ago for a research week. Experts gave talks at night and we participated in one cell sampling. Snorkeled with six whale sharks over two days, then it turned flat calm and they stayed deep. But there's a lot of interesting dives also if that happens. Several not to miss: Blackish Point, Duppy Waters, Pinnacle on the north side and Black Hills on the south. Just off Deep Blue is Pretty Bush, one of the better shore dives in the area. There's also two other sites going east ending up off Laguna Beach.
We looked at Utopia first but they only do 2 dives/day plus shore diving. Deep Blue does 3 - night dives count as your 3rd. Utopia has the best restaurant, our DM told us his family has gone there for dinner - supposed to be the nicest on Utila.
The way Deep Blue runs their operation during research weeks, you dive in the morning while their spotter boat is out looking. Then likely areas are reported to the captain - we found all our sharks on the North side so you've got to be out there to spot them - and it takes a while sometimes - we spent several hours looking daily. Nice thing was the captain let us decide when to call off the search - since ll three AI's are on the south side it's a longer ride back. The north shore is pretty much uninhabited from what I saw, most things are clustered around town in the bay on the south side.
We rode by Laguna Beach daily, seemed like a nice operation. They have a better beach, pool, but I've read the shore dive there isn't as deep.
One thing I noticed is that their overwater cabanas are all on the lagoon side, at Deep Blue rooms are oceanfront but their dive dock is on the lagoon also. Nightly near sunset the sand flies were pretty bad on that side since it's calm and a mangrove lagoon, home owners/operators hack them back for their access but most of it is pretty wild. Our expert went bird-watching there one afternoon, she was so bit up we were kidding her that they wouldn't let her back into the U.S. w/o quarantine.
All three operations are on the opposite side of the lagoon channel so all access to town is via boat. We did see the Laguna Beach boats taking guests into town once or twice (no dive gear) and Deep Blue runs their staff back and forth so it's pretty easy to get there (5mins.) as needed. We took the ferry to Utila but they also meet you at the airport. You have to get to San Pedro fairly early to get to Utila the same night, there's no airport lights so they only fly in till late afternoon. (it's not much of an airport either)