Vietnam and Sri Lanka could both be excellent choices for what you have in mind. Both are best for people who already have experience in these sorts of places, which you do. Twelve days could be a perfect length of time for a classic tour of Vietnam, flying into Hanoi and spending a few days there and in Halong Bay (with a possible side trip up to Sapa), and then taking the train down to Denang for a quick transfer to Hoi An. Hoi An is really a wonderful place and 3 or 4 days there would be great. There are good beaches nearby as well. Then take the train down to Ho Chi Minh City for a few more days before flying home from there. You could also do a side trip to Nha Trang (wonderful beaches) or Dalat up in the mountains. Vietnam really is gorgeous and the food is wonderful (French influences remain) but it can be a bit complicated for new travelers because you’ll find that many people you meet are trying to hustle you a bit, particularly travel agents booking trips and tours. The hotels are generally honest and great value, and so are the restaurants. You’ll learn to ignore the annoying people quickly.
December might be the only month of the year in the Canary Islands where very few people would consider sunbathing. Still, compared to everywhere else in Europe, Tenerife is balmy. The largest and most English-speaking of the Canary Islands, Tenerife is no mystery to the hundreds of thousands of northern Europeans who spend a month or more here every year.
I’m in the Texas Hill Country myself at the moment (Kerrville to be exact), so we are almost neighbors. It really depends on whether you’d like a city or a beach or national parks and such. My first recommendation is Mexico City. You’ll be able to get cheap flights from Dallas, and the weather there in November is very nice and dry. Honestly, the whole huge city center is as nice as any large Texas city, and the architecture is far more interesting. You can even visit some pyramids just a bit outside of town. Before I went I assumed Mexico City would look run-down like many border towns, but it’s actually very fancy.
Phuket is incredibly popular among Europeans in December, especially the final week, of course, so it's critical to book early to get a good price at a beachfront hotel if that's your mission. It's also important to mention that Phuket is an island with more than a dozen different beach towns, each with its own personality and price range. Some are raucous and down-market while others are quiet and very expensive.
Hotel prices definitely go up in around Christmas so it's best to come early in the month if that's possible, but it's still a pretty good bargain even during the peak weeks. Book early if you can because the better and cheaper hotels will fill up first, of course. Also consider a side trip to the Mendoza wine region, Patagonia, or the amazing water falls of Iguazu.
The Bali thing is also kind of a mess for those on low budgets. Kuta is a headache, and pretty much the opposite of what is so beautiful about the rest of the island, but it’s also where nearly all the really cheap beds are located. If you go a bit north in that same area into Legian and Seminyak, it’s nicer, but prices also go up. And Ubud is nice, but also more expensive for hotels and such. I’ll probably rent a place in Seminyak for a few weeks, which won’t be cheap.
In November you can find excellent resort deals all over the Dominican Republic, but Punta Cana is typically the first choice, especially if you are looking for an all-inclusive resort with all the luxury extras at a great price. The resort is actually a collection of little beach areas on the eastern tip of the island, so it's very secluded and well away from some of the confusion closer to the capital city.
Sri Lanka doesn’t really have a good infrastructure for budget travelers at this point. There are loads of nice hotels if you are willing to pay US$40 or more per night, but almost nothing below that except for a few hostels. I haven’t been to Palawan but I have been to Boracay and Palawan can’t be too much cheaper. Boracay doesn’t have many budget options either, so my guess is that Thailand or Cambodia is your best bet.
If an apartment isn’t your thing, or you have to book a hotel for your business trip, then there is one upside: the food. Typically hotels will include some sort of breakfast, and occasionally some sort of dinner plan. In Portland, we stayed at a great hotel that included both. Breakfast usually consists of pastries, waffles and oatmeal – but they almost always have eggs, bacon, and sausage ready to go on your plate.
This French-speaking Canadian city has a definite European vibe, from its cobblestone streets to its quaint boutiques and cafes. The city has a wide array of museums covering interests from nature to stargazing, art, and history. The Montreal Museum of Fine Arts features temporary exhibitions that combine various artistic disciplines — fine arts, music, film, fashion, and design — that are popular around the world. Multi-day museum passes are available.