We enquired about docking fees when we were down there. The only place that seemed available for transients was the Belize "Yacht Club", not actually a yacht club by any means.
The fees were high.
But why not just achor out like everybody else? You're behind the reef, there's no real sea, and no swell at all. If your ground tackle is any good AT ALL, your going to be fine. It's a short row to town (hell you can swim half way and walk the rest), there's not much in the way of big wind shifts.
When we sail down, that's definitely what we will do.