We just returned from a week in costa rica. Was looking at visiting Belize in mid September for a week.
Our main purpose is to see the Great Blue hole.Might do some snorkelling.Visit Cockscomb Basin Wildlife Sanctuary & .Crooked Tree Wildlife Sanctuary,ATM cave tour and see the hummingbird.Can do a self drive.Any suggestions welcome in terms of lodging and tours.

isn't that the rainy season?

Rainy season from June to Jan, but Sept, as a rule, is not known for high rainfall.

Yes it is the rainy season but it IS still possible to go. My husband and I went to Belize The first week in October of 2013, also during the rainy season. The only issue we had is if it rained too much, we would not be able to do the tubing activity down the river b/c of water levels. I am not sure how it would affect diving, and ultimately, the rain didn't affect us. It is a gamble, but it was worth taking for us - plus the "off season" rates were great. We stayed at Sleeping Giant in the Jungle and Jaguar Reef for the beach. SO, SO WORTH IT! HEre's I think the package we did:

http://www.vivabelize.com/packages-s...ation-package/

You also might want to check Groupon - they often have vouchers for Belize. A few couples had used them to travel at the same time as us and had great experiences with it.

All months are rainy in Belize...if planning a trip expect rain..just a fact of life down there..you may get lucky

The poster above is not a gardener or farmer. April and most of May should be bone dry. Other months can also be dry. Mid Sept is not a rainy month for the most part. I will have to water the plants.

How many nights? 6? What's your budget? Any interest in Maya sites? More info will help us help you. In the mean time, my photos with blog, travelogue, and review links on the main page of each collection are below in case you're interested - all my recommendations are embedded there. Happy trails!
http://www.flickr.com/photos/staceyholeman/collections

Thanks for the suggestions. we are now looking at April 2017