It looks very likely that we'll be heading to Vietnam this year for Christmas and New Year's, because I found some great flights into HMC. We'd have 18 days, and I've never been to Cambodia, so I'd really like to split the time between Vietnam and Cambodia. I think the only places I've been in Indochina are Bangkok, HMC, and Nha Trang, and my SO has never been to SE Asia at all.
So lay it on me!
What are your top recommendations? What is your advice? Do you have old trip reports and blog posts you want to share?
How easy is it to get around by land transportation? Are there comfortable long-distance buses? Is it easy to book sleeper trains, and how far in advance do you need to buy tickets?
What about accommodations? Is it easy enough to find budget accommodations (think inns, 2-star hotels, or private hostel rooms) on the fly, or should we sketch an itinerary and book in advance?
Would it be worth the ~$100/pp/day to spend half the time on a backpacking-style group tour that would include overland transportation, lodging, and sightseeing? (What if it was only $75/pp/day? [SO may have unspent travel allowance that we could use for part of that.])
I have a blog post that covers Thailand and Cambodia (just Siem Reap) if you'd like to take a look. I won't be too much help with your particular questions, though, because we flew everywhere and the hotel we stayed at in SR was a nice boutique hotel that was a little more than $100/night.
I'm also going to be keeping an eye on this post because we just decided to go to Vietnam! We're still working on dates but it will probably be March or April with a stop in Taipei or Seoul (mileage ticket routing).
Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime. Mark Twain
I really loved Hoi An. I wish we would have spent more time there.
I'm not sure about inns, etc, but we booked in advance. If you want a hotel rec, we stayed at multiple properties from the Victoria chain (Sapa, Hoi An, Phan Thiet and Can Tho) and had a great experience at all of them. www.victoriahotels.asia/en/
H and I did a half day spa at the Hoi An one and even with a 20% tip it ended up being $75 total.
We booked a private driver to drive us to some cities and flew between others. The roads are ok, but expect it to take you a long time to go a short distance.
When we went (2009) the only way in/out of Sapa was via train, so we booked a 1st class sleeper train there. It wasn't the worst thing I experienced, but I also never went to the bathroom on the train. H told me only go if it was a true and dire emergency. I remember the pillows smelling a little mildewy too. We ended up taking sleeping pills and passing out for the journey into Sapa.
IMO, you don't really need a guide or a group, but it just makes it a lot easier. Most people don't speak English, but everyone's super friendly and nice. Usually someone around will know enough to help you, if you get stuck.
I was in Cambodia, Laos and Vietnam over Christmas and New Years a few years ago.
It was pretty hot and humid in Cambodia but not as wet as when we were there in October th previous year. We only were there to see Angkor Wat which I highly recommend.
Honestly I would skip Vietnam and go to Laos, Laos is so much better. But if you're set on Vietnam, we stayed in Hanoi. I was shocked by how cold it was in Hanoi when compared to the humid and warm Laos and HOT Cambodia. I had to buy a sweatshirt in Vietnam. We were in Hanoi right before the New Year and the hotels were hard to find, everything was booked. We managed to find a spare room above a restaurant. It was sort of a storage room with a bathroom that they kept their extra chairs and crap in but it had a bed so we took it. We went out to Halong Bay and spent NYE on a junk boat. My MIL then severely injured herself on a bicycle the next day and the trip pretty much ended right there, she spent 11 days in the French Vietnamese hospital in Hanoi. Our original plan was to travel down the coast and hit up the beaches but that was scrapped, it turned into a 'how are we going to get her airlifted out of this country' type of trip.