I would recommend Banyan Bay as well. Since it opened a few years ago, we have rated it at or near the top among the condotels on the island (four stars). The BYC has gone through many changes -- condo, timeshare, meeting hotel, and combo of the above -- and has had various problems between condo owners and management; one never quite knows what to expect, though the location is excellent and some of the units are beautiful. Banyan Bay is also on one of the best beaches on the island, whereas BYC really has no beach, just a seawall.
Another option at a lower price is Banana Beach, close to Banyan Bay. It has only one-bedroom units, but these are very nice, especially the seafront units, and the rates are much lower than either BYC or Banyan Bay, especially if you book direct.
Belize First Magazine http://www.turq.com/belizefirst/