I plan to purchase a condo at Green Valley, NV.
Does anyone know those area ?
What were you looking to find out?
Years ago GV sprouted up and is now a fully matured area. It is pretty good over there. Like all pockets around the Vegas core, it filled up with residents.
They have a nice mall over there 
Summerlin and Green Valley are 2 good areas.
Yes.
Summerlin (where I live) is the best development/community. As far as appreciation goes, Summerlin and the many areas in the SW are the kings. GV is up there as well.
Whats the zip code? The best way to do research is by zip code. If the only info you have is the area of the city, I suggest you might want to get the zip code, go to the the Las Vegas Board of realtors web site (free), plug in the zip and see what the comps look like