Within a few hours you can be in Rocky Mountain National Park. Plenty of routes up to that grade for you to do. What's your M grade ability?
Officers gulch is another area nearby but will likely have high avalanche danger that time of year. There's a number of good climbs within your ability there, and if conditions are acceptable it's worth considering.
Vail is filled with great climbs up to WI4, but the parking situation is a bit of a hassle.
Lincoln Falls is a reliable flow of ice about 2 hours from Boulder on the Northern side of Mount Lincoln. Mostly WI3 climbs at Lincoln, as by then the steep pillar that forms will usually be either hacked to death or sublimated away.
I think any other areas (Lake City / Ouray / Silverton / Eureka) will likely be too far away to consider. However all that should keep you pretty darn busy I would say.
With a couple of exceptions, the approaches in RMNP are long, especially if you are not acclimatized. There is also avalanche danger to consider on some climbs. I've encounterd a lot of climbers unfamiliar with the area hiking out with their tails between their legs. Just do your homework before starting out and know the trail conditions and avy danger. President's weekend is likely to be busy wherever you go.