When I add a smoke particles (clouds) it seems to be thick and an a certain elevation. I'd like to have thin clouds around the tops of buildings. Is there a different method?
You could try the Cloud Generator addon. This is good for making 3D volumetric clouds, but note that it will only work for BI, as cycles does not yet have volumetric rendering.
Enable the Cloud generator addon in User preferences > Addons. This addon is bundled with blender by default, so it should be in the list:
Create a bounding shape for your cloud, then press Generate cloud in 3D view > Tool Shelf (T) > Cloud generator with it selected:
This will create a point cloud for the cloud and setup the volume materials.
For more info take a look at this tutorial on blender cookie.
Because cycles does not yet have volumetrics, you will have to fake it. Here are some options:
Render the clouds in BI and mix in the compositor
Use a transparent plane with an image texture (may look okay when seen from a distance)