Evaporative Water Coolers - Evaporative Cooler or Air Conditioning?

I live in Longmont Colorado and own a 1970 built tri-level house that I have cleaned up and remodeled quite a bit. Unfortunately it never had a cooling system installed and has hot water baseboard heat, so there is no ductwork for A/C, I would have to pay to have that installed.

I have received quotes from local HVAC contractors and they do not agree on the best way to install A/C. One says go in through the attic and one says go in from the crawlspace. Either way it will cost between $8-10,000!
Yikes!!

After hearing that we started looking at Evap Cooling, which would cost about $4,000. Much better price. My questions are to those who live in this area: Do evaps work here? What about cooling the whole house sufficiently?
I know the principle way they work, that you open windows a crack where you want the cooling to go, but should additional venting be installed to those areas, and should they be installed on the north facing roof of the house? What if they don't work correctly, can I come back on the contractor to fix the problem?

Someone with experience in this area please answer.

Thanks, Mary

Its more in what you want. Also how clean do you want the home. You could go for a whole house fan. That way suck in the air at any window you want. Or the Evap Cooling. That will put a high humidity in the home . Or the AC that will take out the humidity an help keep the home clean. Id go for the AC with the duct work in the crawl space.