The national road from Sandu to Congjiang passes through the Duliu Valley. The scenery on the way is so beautiful. A hike is also rewarding.
The town is small enough to get around on foot.
It stretches mostly along the river so there really are only two big streets, one on each side of the river. On the northern bank is the busier National Road. On the southern side you'll find shops, street vendors, a market and at least one bigger-than-a-kiosk sized supermarket.
Like in other cities in the region you'll see traditional wooden Dong houses mixed in with modern Chinese buildings (modern as in built in the 80's). There are whole Dong villages right behind the row of Chinese buildings along the streets.
If you start near the bus station (northern bank) you could take a cab to the outdoor food market, which is on the other side of the river and west from the bridge. From there you can stroll back in 30 minutes or so.
You'll get a nice view of the traditional Dong settlements from the southern bank of the river. If you go up the stairs behind the houses across the bus station (for example) it's almost as if you're getting into a completely different, rural village within a few minutes.
There are also pagoda-like structures, which make for a good destination for exploratory hikes. Those are not actually called pagodas (塔), but the author can't remember the correct name. Locals should understand what you mean though and correct you.
There are many little restaurants around the train station like you would imagine.
The outdoor food market is also a very nice setting for lunch.
There are several Hotels (mostly Binguans) around the bus station that should all be reasonably priced and have air conditioning.
The new expressway is now finished and open to traffic. The Congjiang intersection is roughly an hours drive from the bus station along a very poor quality road. However, once on the expressway, the traffic is light and the speed is fast.
The bus from Congjiang to Sandu goes along a windy road through the mountains and many small cities. The landscape and the minority inhabited small towns kind of make this a worthwhile sightseeing bus ride. Sandu is now accessible via the new expressway.
Buses to Guiyang take 4 hours (¥150) and leave twice daily, the last is at 10.20am. This journey cuts right through numerous minority villages and provides amazing views from the high bridges.