In addition to n'w'er's questions, is shade involved? Are you on a (north/south/east/west)-facing side of a hill, or is this more like flat prairie?
Generally late summer is the right time to seed cool season grasses to avoid weeds and to have a strong root system going into summer. You missed that opportunity this year. For most people late summer is when the evening temps cool off. At high altitude and low humidity, I'm not sure when to peg that time of year.
You live in a sweet spot where the following grasses grow: crested wheatgrass (look for Ephraim and Fairway) western wheatgrass, streambank wheatgrass, and blue grama. These are prairie grasses but when seeded fairly densly and mowed, they look like a real lawn. Here is an example from Salt Lake City.
This lawn also has a little strawberry clover as you can see in the very front of the image. Note the dark green color. The owner of that lawn was doing an experiment to see if he could create a lawn that needed very little fertilizer, mowing, and water. He starts watering sometime in June and sometimes only waters 4x per season, he does not fertilize, and only mows monthly. All these grasses need full sun to survive. If you have any shade, none of these grasses will work for you.
If you are in a shady area, your only alternative would be fescue. If you can find fescue sod in the spring, you can safely put that down then. Otherwise I would tough it out with the weeds until "late summer" and then seed the fescue.
Here are the 1-2-3 basics of lawn care.
- Water deeply and infrequently. Deeply means at least an hour in every zone, all at once. Infrequently means monthly during the cool months and no more than weekly during the hottest part of summer. If your grass looks dry before the month/week is up, water longer next time. Deep watering grows deep, drought resistant roots. Infrequent watering allows the top layer of soil to dry completely which kills off many shallow rooted weeds and prevent new (weed) seeds from germinating.
- Mulch mow at the highest setting on your mower. Most grasses are the most dense when mowed tall. Bermuda, centipede, and bent grasses are the most dense when mowed at the lowest setting on your mower. Dense grass shades out weeds and uses less water when tall. Dense grass feeds the deep roots you're developing in 1 above.
- Fertilize regularly. I fertilize 4-5 times per year using organic fertilizer. Which fertilizer you use is much less important than numbers 1 and 2 above.
Note that if you have the wheatgrass mix, you can probably skip most of that fertilizer. Otherwise, I have been using alfalfa pellets (rabbit chow) with great success. Search this forum for a picture showing the effects of alfalfa on a lawn.