The only one of the above that I have been to is Cuba and but a lot depends on the sort of things that you like doing on holiday. If you could perhaps give us all some more info the sort of things you like to do on holiday and on other destinations you have been to and liked? I ask becuase you seem to be torn between two very different sorts of holidays ie between a 'drop and flop' AI holiday and a tour where you get to do a lot of sightseeing.

As for Cuba it doesn't need to be a 'drop and flop' AI because theisland hasmuch more to offer than that. I can't comment on the merits of the hotels you are looking at because that isn't my sort of holiday in Cuba but you should ber in mind that on the Cayos there is very little outside of the hotel because those with the big hotel compelxes on them are otherwise inhabited. Also you won't have any that much freedom to book anything other than the TOs excursions (actually provided by one of the state owned tour agencies) unless you are confident about doing them on a DIY basis. You won't find the smaller private excursion companies that exist elsewhere and enable you to undercut those offered by the reps.

You will however, find fantastic beaches, especially on the Cayos but in the whole the big AI hotels have been built where they have because of the beaches so you probably can't go wrong on that count. As for snorkelling then there are people around on HT better placed to comment on that but I have never got the impression that this is anything exceptional.

As for weather, well you are starting to get into the hirricane season at that time of year but if I was having to travel then (and 5 out if my 7 trips to Cuba have been during the Hurricane season) then Cuba is one of the few places in the Caribbean that I would consider travelling to at that time of year because their safety procedures are 2nd to none. You'll find much more info on that within the Cuba forum. Expect it to be hot with growing humidity the later you go and hence with the risk of a bit of rain but it tends to take the form of short heavy showers that soon clear up.

I am a confirmed Cuban addict and I think that it has lots to offer, including great places to see and visit but you will get the best out of it if you look at the sort of itinerary you are thinking about for Thailand, Singapore and Bali. It will be tight on your budget if you go for a bespoke tour organised by a TO but it would be possible if you are confident about doing it DIY and especially if you can speak some Spanish.

SM

SM

I've been to Thailand, Bali and Singapore. Would you really want to go to Koh Nang Yuan for six days its really just three islets joined by sand bars - spectacular for a day trip or a couple of nights with good snorkeling but not much to do for a whole week apart from trips off the island. Samui of course is much larger and has more in the way of attractions.

You are picking the right time to visit those Thai islands weather wise.

As for Singapore and Bali, again not a bad time to visit. Beach wise Bali is OK but I think Thailand has the better beaches. Nusa Dua while nice is very much a manicured tourist enclave.

Singapore of course is more a city break, an expensive destination compared to Thailand and Bali. Plenty of man made attractions to visit, but some find it soulless. I quite like it though as contrast to less developed SE Asian destinations.

Thailand
I would suggest that you keep most of your Bangkok time till the end of the holiday. Bangkok is easy to get around but it can be a bit overwhelming with jetlag. It's a fantastic place. Going with what Sunbear says- more time in KS. Bophut is a great place to stay- lovely restaurants and bars along one road( and the beach) and within 10 mins taxi to Chaweng for more lively evenings. ( probably depends on your age- you may prefer to stay in Chaweng)

Bali
I was surprised when we first went there. I had always assumed beautiful beaches with miles and miles of golden sand. However, I loved Sanur beach as there is so much to see. You really do share the beach with the locals- watch the children flying their black bin bag kites; fisherman standing in the sea, or boats being painted and nets mended; women making and laying their daily offerings to the gods, either on the sand or at a shrine. Ubud- glad you are looking at spending time there. The evening Temple dances are magical. Nusa Dua- really not keen on it all but we can't all like the same things!
Singapore- very, very expensive. I would cut down on your time there. To be honest, 3 or 4 days is enough. I do love the city though- completely different from Bangkok, but lots to see and do. You can offset the expense there with the cheap prices in Bali.

Cuba
not been but Sma is the expert

Mexico
We have gone twice in the summer. Loved it for just total relaxation but it would be a bit like Cuba weatherwise and so therefore can be more of a gamble than Thailand and Bali. We managed to miss the path of a hurricane the first time we went but only really had one bad day. Second time- a couple of completely rainy days and a few showers in other days but it didn't spoil it too much.