Hi, I will be in Vietnam for 5 weeks and plan on doing a fair amount, but I am not rushing around. I would like to choose between the Ha Giang area and Dien Bien Phu. I am going in July. Leaning towards Ha Giang, but maybe weather will be a problem. This may be a stupid question, but how could I get good specific weather info and travel warnings about Ha Giang in Hanoi before I go? What would be a specific detailed source that bus travelers could use? Also, not sure I have time for Ninh Binh. Is that a mistake? Thank you.

DBP is interesting only for people who like History ; not much left to see about the battle except Eliane 1 Hill, the HQ of General de Casties, the HQ of Giap 25 km away, and a nice museum. The region north of Ha Giang (Quang Ba/Dong Van/Meo Vac) is FABULOUS. Go there ! For weather, just type "meteo Dong Van" on Googles and click on "Accuweather"
What I remember most about DBP was the journey to and from which was spectacular and makes one marvel at how the N Vietnamese ever got all the equipment and men into position. I also enjoyed walking out in the hills around the town. I agree the town itself was not noteworthy
You ask about Ninh Binh but hard for anyone to tell you if it would be a mistake to miss it especially without an understanding of what would have to be missed
Is it easy to explore Ha Giang (and Cao Bang) if I don't drive motorcycle at all?
Yes. Either get a bus to Ha Giang then hire a bike + driver from the likes of QT (google QT Ha Giang) Or just use local buses to get around then pick up a xe om anywhere you want to explore.
Been to Ha Giang region 4 times so far and would happily go back 4 more. Been to Dien Bien Phu and all the way out to A Pa ChảiSín
There's a lot more bang for your $ in Ha Giang. Nobody who has been there has ever left disappointed.

You g to Ha Giang or Cao Bang by night bus and then minibus HG-Dong Van or Cao Bang-Bang Gioc. If Dong Van, you rent a taxi or a scooter driver for one day to go to Lung Cu and Saphin and up the fabulous Ma Pi Leng Pass up to Meo vac (no minibuses)
There's a lot more bang for your $ in Ha Giang. Nobody who has been there has ever left disappointed.
Really?
Anybody who leaves Ha Giang with disappointment probably carries around their very own bag of disappointment.