Blue Tang is the new name of Rock's Inn, right? This is a place that has long cried out for better management, and almost anything would be an improvement.
As to Trends on Caulker, depends on which Trends you mean. The Trends Beach Hotel at the main pier is a couple of years old and is a good value at around US$30 a night -- small rooms but clean and neat and in a good location on the water (though busy with all the traffic at the pier.) The original Trends is cheaper but not on the water.
Spindrift is a hulking concrete hotel in the middle of San Pedro Town, on the water. Variety of rooms, none fancy, but I kinda like the place. As others have said, in the budget category Ruby's is the clear popular winner, but Spindrift isn't a bad choice in the low moderate category.
Belize First Magazine http://www.turq.com/belizefirst/