As a frequenter of the Rockies in CO and WY I would advise against a hammock. Many of the campsites that you will find will either have no trees or no suitable trees for hanging up your hammock. If you plan it right it would work by camping lower in elevation but I have never liked to be limited in where I camp.

From your description just get a lightweight 2 man tent or a tarp tent. My current 2 man weighs 4lbs and can be setup with just the fly and footprint to knock off more weight. It seems like every place I go has mosquitos so I personally like to have mosquito netting.