Oh I have to rise to this one as a passionate fan of Ambergris Caye.
I'll start from the north and head down. You start with a magnificent nature and marine reserve, Bacalar Chico. This reserve is about where the reef meets land with spectacular results for anyone interested in marine life. The nature reserve has its own campsite and education centre and many people don't realise the diversity of wildlife here until they have experienced it. We have Jaguar, Jaguarundi, Margay and maybe Ocelot (I'm not sure). We have peccary, deer, ant eaters, snakes, lizards and so many more species I'd suggest you read the field guide //ambergriscaye.com/fieldguide/ to get a real perspective.
So you head down the coast and you start to see resorts and houses. This part of the caye looks like the real fantasy, caribbean paradise that everyone dreams about. Tall swaying palm trees, beautiful beaches, charismatic resorts with a few houses of different types and architecture interspersed. Many of these resorts have top notch restaurants and of course the access to amazing marine life is always apparent. As you get closer to 'the cut', you'll notice an increase in the number of residential properties, see the gorgeous area of Tres Cocos and the bridge so you'll realise you are approaching the town of San Pedro.
Before the actual town is a bustling and lively residential area containing a well used waterfront park called Boca Del Rio. This area is full of local life, great little eateries and shops. You then hit San Pedro Town itself. A small, bustling little town with cobbled streets, a wide variety of shops, friendly people and a lively nightlife. Make no mistake. San Pedro is a small town and no longer a sleepy village and with that comes the good and bad. Traffic (if you can call it that) can be busy at rush hours, but most people still travel in golf carts, on bicycles or on foot. There are taxi vans, some cars and SUVs and motorcycles, but for the most part, the use of golf carts and bikes makes traveling around town a social event, with lots of waving, stopping and chatting. Anyone who lives here knows that a trip to town for one or two items can end up taking half a day because you see so many friends along the way that you can't help but to stop and talk and catch up with the town gossip.
San Pedro has an active town council that keeps us all entertained with regular events for every holiday. There is always something going on and never a reason to be bored. The shopping and choice of places to eat is sublime with everything from wonderful home cooked local dishes to international cuisine such as sushi and authentic Italian available. With two nightclubs and many bars on its three main streets (front, middle and back street) the nightlife is exciting and especially during tourist season, great fun for everyone. Compared to most small towns, San Pedro is an incredibly safe place for people to relax and let their hair down in.
As you move south you will pass more interesting and eclectic resorts, each with their own character and most with bars or restaurants on the beach. There are plenty of beautiful beach homes as you go south as well as large residential communities. Many people who work in the town or own businesses there live to the south because of the ease of access to town without the need of a boat. The further south you go, the quieter it gets, with houses spread out and much more open land. There is a great deal of wildlife at this end of the caye as well and it is easy to spot birds, crocodiles and a whole range of fauna as you venture south.
Eventually you get to the very end, which is where the last bar on Ambergris Caye sits, Ras Safari. You can cycle or cart down to this area and fish in the channel for a real get away and you are going to definitely be able to catch your dinner here with snapper and barracuda easily caught.
I mustn't forget to mention that you can always see the beautiful reef from San Pedro, swim from some of the beaches (not all as some are such great habitats for sea life that they have turtle grass and a soft bottom, which helps to keep the reef alive), kayak in the still shallow water inside the reef and snorkel wherever you please.
I know I've left a ton out of this because there is so much more to love about Ambergris Caye. I'm sure others will fill in the gaps.
Ambergris Caye 
Just for discussion. I only visit AC to pay my dues at Im. the place is to busy for me. I/we, wife and I, prefer the village atmosphere of CC. It is a true village with all the exciting dynamics plus the Belizian culture and politics. Oh the politics! I still don't wear red or blue shirts. Soon everyone one knows of the new guy, just like any small town. Soon you too come to know all the players.
AmbergrisCaye.com