This upcoming December my girlfriend and I are planning on traveling to Japan and then head to Vietnam's Mekong Delta region. We were thinking of starting in Can tho. Our plan was to set up shop in a single location in the Mekong Delta, enjoy that city/area and do day-trips from there.
Does anyone have any other suggestions, and how much time should we plan on spending there?
I'd suggest moving your base around a little - Can Tho is a good starting point, but the Delta is at its best early in the morning, and you'll miss out on seeing other places at /their/ best if Can Tho is your only base.
There aren't really any of these major 'must sees' that I keep hearing about in the delta, it's more about the countryside and people getting on with their lives on the land and water, but I've spent up to about a fortnight in a single visit in the delta without running out of things to see and do. Plenty of exploring to do. I'm a slower traveller than most, I think, but you could easily spend a week or so....
You can expect great weather in December - make sure you get a couple of days on the beach if beaches are also your thing.
I agree with the above.
Can Tho is a great starting point. The little riverside park is great to see life go by and see the Vietnamese enjoy the evening. An early boat trip to the floating markets is a must when there. Although check up on that because I've seen some strange reports here.
Afterwards it's up to your interests. Can Tho town itself, although charming in parts, is just a big commercial hub. It's the countryside around it and the rest of the Mekong that is most interesting but only if you appreciate the smaller things in life and just would like to see how the locals get on with their lives. I already like the numerous ferry rides crossing the many rivers.
Perhaps rent a boat during day time or do a home stay at a farm. I've never done that but it could be fun. You can also book day trips visiting (fruit)farms but those (I've done 3), while interesting, are touristy. If you have the time and money you should try to organize a private trip to visit these farms.
I'll be in Can Tho next week for a short visit and will check if there's anything new.