I stayed at Mata Rocks in May 2006, and enjoyed it very much. Their off-season rates were a real bargain -- and I see you will also be there off-season. Clean, small complex, with every unit having a sea view.
I'd stayed at Belizean Shores in January 2006, and loved it, too. That was a large condo, whereas Mata Rocks was a small accommodation. Both were great choices, top-notch for their niche in the lodging scene. I enjoyed walking to town from Mata Rocks -- did it every day. Not possible from Belizean Shores, but the water taxi worked fine from there.