I haven't been to Da Lat since 2009, but when there we stayed in Peace Hotel for $10 and I thought the rooms were very reasonable value. We were there in August and you're right, no need for a/c, but rooms had a TV and balcony overlooking the street.
Have a look at AGODA.com
I booked all my hotels for Vietnam through them, Got one in Dalat for $11.
Sorry cant coment further as my trip is in July, but have a look at the site.
#5 MsMalika has been a member since 19/5/2011. Posts: 7
Think over about the hotel with 10$ in this summer 2011 in Vietnam. The weather is hot, so that you should make sure that your hotel is cool enough with air-conditioning. Choose another choice because no one is sure about the quality of the hotel with 10$/net. If you are lucky enough, you will be satisfactory, if not the night seems to be a nightmare.