My wife and I did the Altun Ha trip last May. We booked with Hustler tours, but I believe we actually toured with another outfit because Hustler didn't have enough people to go out on its own (this seems common).
In retrospect, the tour was a good experience, but it is not the most comfortable experience in the world- it is very hot, the trip is long, you see a lot of rural poverty (which is an eye opening experience) and you don't see as much wild life as one hopes.
However, the ruins were interesting and it was a good trip to just experience how other people outside the US live day to day- we are very blessed in the US.
I wouldn't do it again and would rather spend my time and money doing a couple more snorkel outings. However, if you have never done something like this before, you should consider it.