Da Lat (or Dalat) is a lovely little place which I found difficult to leave. Like many of my favourite places around S.E. Asia, there's nothing obvious to explain why I liked it but it was more to do with the feel of the place along with the people (both locals and fellow travellers) and a few activities.
Food
Please use my Vietnam food guide which has all of my favourite places and dishes for the best food in Da Lat.
Accommodation
Dalat Backpackers Hostel And Tour Office
New in 2014, I think, it had come recommended to me by other travellers. When I was there, a lovely couple from near Brighton were working there. There's a welcome meal every evening for the guests who arrived that day. You all sit around in the reception area and get a mixture of dishes (though it wasn't enough food if you're hungry). It's a great way to meet people. There were about 12 new people when I arrived (more than normal) and we all signed up for the canyoning together. There's also a great rooftop area (which has been improved since I was there) where you have your free breakfast and everyone tends to hang out and drink at night. My room was massive and was $9 per night. There are dorms too (which I slept in when I arrived at 5am after a night bus).
Nightlife, bars & cafés
Me Linh Coffee Garden
Picturesque plantation with tasty coffee that's been pooped out by weasels (which you can see). Although animal welfare is an issue.
Sights & Activities
Crazy House
The very strange Hằng Nga Guesthouse is open to the public (for a small fee) during the day. In 2009 it was listed by a newspaper as one of the world's ten most "bizarre" buildings. It's like a cross between Gaudí and something from Disneyland, but weirder. There are staircases going all over the place.
Dalat Market
In the centre of the town is a large indoor market for cheap clothes. At night there are lots of food stalls outside.
Canyoning Dalat
The best $20 you'll spend in Vietnam! A full day of abseiling down waterfalls, cliff jumps and other amazing activities. I booked mine through my guesthouse and did it with a big group all staying there. It's very well known around town, you'll find it easy to book wherever you're staying. Bring appropriate clothing and footwear as well as a GoPro if you have one!
Transport
Easy Riders Vietnam
There are loads of companies in Da Lat calling themselves Easy Rider(s) so try to do some research to make sure they're good. I did mine with Dalat Backpackers. It's expensive ($70 per day for the motorbikes, guide and accommodation) but totally worth the amazing experience. I did a three day tour from Da Lat to Buôn Ma Thuột and finishing in Nha Trang. I had planned to buy a bike and do it myself but ran out of time in the end. Having a guide is so valuable, he took us to places I'd never have known about. You get to ride a proper manual motorbike rather than a scooter and the guide carries your bag. If you're not comfortable riding yourself then you can go on the back of the guide's bike. Highly recommended if you can afford it!