I've spent 2 winters in Mui Ne, here's my 2 cents:
Most people call it Mui Ne but in reality they probably should say Ham Tien when they indicate the touristy spot. This touristy spot consists of mainly one main street - Nguyen Dinh Chieu street - that runs all along the beach. On this strip you can find plenty (PLENTY) of hotels, guesthouses, appartments, private houses and then all the restaurants and shops. There are mainly Russian tourists, prices for food are cheap by Western standards (rice and veggies meal for 2-3 euros, beers from 50 cents and up, but like anywhere else you can spend as much as you like) and locals are very friendly. There are a number (more than 10 for sure) of kiteschools/kiteclubs where you can rent/learn/store. Basically almost every waterfront complex (hotel or appartments or similar) has a kiteschool/kiteclub on the beach in front of it. The water conditions and wind conditions are a little different from Mui Ne/Malibu Beach (see below), but the "good" season is similar. In Ham Tien the water will be more choppy/messy overall and it has quite a strong/big shorebreak, which can be problematic for beginners. Because of all the schools there's a lot of kiters, but it's not annoying there's enough space for everyone. The windy season starts sometime in November and ends sometime in March, with the peak being end December- February. Like anywhere else: if you're lucky you can kite everyday, if you're not then not. (We had awesome days early December!) On good days wind picks up in the morning from 10-12, then gets stronger, peaks around 15:00 for some time, then slowly dies down , but I've had many sessions until sunset. Average size for me: 9 ( I weigh about 72Kg). Many times smaller in the afternoon. You might need a 12 for the mornings or light wind days. Ham Tien is definitely best for twintip kiters and the odd foiler in the mornings when wind is not yet strong. I personally really like Ham Tien because life is easy there: You just rent a little motorbike, you kite everyday until sunset, then you shower, you go out for dinner and you sleep. Rinse and repeat. Oh and if you need gear you'll find whatever you need: there's a North (Duotone?) shop, you can find kiterepairs for cheap, there's a Shinn dealer, and also a local facebook page with gear for sale (check Mui Ne buy and sell on Facebook) and even more shops (quiksilver, rip curl, 69 slam etc). A 20 minute drive by motorbike to the north-east is the actual fishing village of Mui Ne with Malibu Beach right behind that. There's no real "gap" between Ham Tien and Mui, it's just one straight road from the center of Ham Tien to Mui Ne, with restaurants, hotels and shops and houses all along the way. Mui Ne itself is of no interst to me, but Malibu Beach is great: better for strapless kiters because more, better and bigger waves. Wind is also a little stronger, I had to use my 6 several times, otherwise mostly my 8 and sometimes my 9. The beach in Malibu has a couple of expensive resorts and in front of them you can kite. Same story: kiteschools in front of almost every hotel. Malibu beach being smaller than Ham Tien, there's less hotels so less kiteschools and less kiters. Again, mostly Russians, which is fine, they were all very nice and friendly. However Malibu Beach doesn't have the night life of Ham Tien. I stayed in Ham Tien and rode my motorbike to Malibu each day, having found storage for my gear in one of the many kiteschools.
Then there's also Phan Rang, about a couple of hours driving north, maybe 3-4 hours drive, depending on the driver and traffic etc. This is a lagoon with butterflat water inside and some small beginners waves outside. Last year there was only 1 or 2 kiteschools, this year there were 4. The water can be very shallow inside the reef so check before you go, sometimes it's really not enough. Look for Phi KiteSchool Phan Rang or others, they should be able to tell you when the tide is OK. Wind in Phan Rang is stronger than Malibu and Ham Tien but also a little more gusty. I used 8 and 6, and 9 for earlier sessions.
All in all, between these three spots you should be able to kite a lot, unless you're unlucky windwise...We've spent 2 winters with almost everyday wind, except when our friend came over for 3 weeks: he had maybe 1 in 2 days wind overall.
There's a fair bit of pollution visible everywhere (like in most of Asia), and also in the ocean (plastic bags and other rubbish, especially around fullmoon periods and high tides) so be prepared for that.
PS: try the foodcourt Dong Vui, it's a great place for dinner and some drinks
Oh almost forgot: water's warm, no need for any suits, just lycra for sunprotection and hat for same.