We do the trip over to Isla Mujeres every trip, and highly recommend it. The Boobs Cruise is mostly about being on the boat, while the day trip is about being on the island. The ferry is only a 10 minute walk from TTR.
Had that room before and it is a great room. But like everyone else says express check in doesn't help too much. I usually put in the remarks box when doing the express what room I would like if available and the last 3 times I have been able to get it. Most likely just luck though.
The one thing about Isla Mujeres I didn't like was that they charge you to use the public restrooms. I forgot how much, maybe a dollar, but we hadn't brought any cash with us (our booze cruise was a spur-of-the-moment thing)
