Beach Bound, I stayed two nights last May. It's a beautiful place - quiet yet only a 40 minute drive from Belize International. The food is world class and the spa treatments are too. It's pricey but you get your money's worth. I went to Altun Ha with one of their guides. I was with one other tourist and we were the only ones there (large groups come in the afternoon).
Last year the round trip transportation was $50 per person - so it's gone up. For me it was cheaper than a round trip taxi ride but for two or more people, the taxi would be the way to go (sorry, I have forgotten what the taxi fare was).