Is Sahara desert a good place to build radio/optical telescopes? At least Atacama Desert of northern Chile is a good place to build telescopes.

VLT and ALMA locate there.

What about Sahara desert?

http://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array

http://en.wikipedia.org/wiki/Very_Large_Telescope
No, the Sahara isn't a good place to build telescopes.
The Atacama desert is used because it is at high altitude, which means that there is less atmosphere to get in the way. Other telescopes are located on mountaintops for the same reason.
The Sahara is mostly at sea level. It's also very hot, so you get lots of turbulence due to rising air, which distorts the image.
The Sahara is also undesirable for other reasons: no infrastructure, unstable regimes, lots of erosion due to sand storms.