There are dozens and dozens of individual condos and condo/hotels on Ambergris Caye to choose from. Where you choose to stay really depends on your budget and how close to town you want to be.
This link lists most of the condos available. Take a look and then let me know which ones seem to best meet your needs. Then I'll be able to guide you in making the best choice for your upcoming trip to the island.
What I have found is that most people fall in love with the part of the island where they stay the first time they're here. So if you are looking at property on the south side of Ambergris Caye I recommend you stay there. If on the North, stay up there. This way you can test drive the area of the island that you are looking at owning.