There used to be a Waldorf school in SLC, but it closed down nearly 2 years ago due to administrative problems. I believe there's sufficient interest for a Waldorf school--though unless you get outside funding, it will be priced along par with other private schools. My understanding is that the school was not able to retain families because of the administrative problems, so there was a high attrition rate, which kept enrollment numbers down, which, eventually, made it fiscally impossible to continue.
I would love to see a new school started. However, the effort will need a lot of new blood, since the old-timers have been around the block a couple of times and don't have the energy to carry it all themselves, plus it would need enough families committed to it--and to paying for it--to continue. ASWANA has some guidelines for starting a school here: http://www.whywaldorfworks.org/02_W_Education/faq_starting.asp
I suspect if you could get a grant or a donor to help fund the startup costs, that would solve a lot of problems. You will need to pay for a couple of certified teachers--apparently they're in high demand--and find a suitable location to rent or buy. I also understand that the original attempt to start a Waldorf school as a charter was thwarted because a lot of people saw it as a religious school and therefore inappropriate to receive state funding. You might be able to get around that if it were done right, with the right education and public outreach.
I think something located either near Sandy (to attract both SL and Utah Co. residents) or somehwere mid-SLC valley would probably be the most sustainable, unless you know you have a strong group in Utah County. Most of the people I've talked to who are interested in Waldorf are in SL or Davis counties--but then, I live in SL county, so that probably has something to do with it. I'd love to help get something started and support it--I have a 4.5 yr old and I've been interested in Waldorf since before she was born. But we'll need a full-time banner-carrier to pull it off.