I disagree with your friend's comment that Denver is not bike friendly. In fact, I think it surpasses Tucson. Yes, the busier roads in town don't have a shoulder like in Tucson but there's no reason to take them. I don't even like riding those when we've stayed near Oro Valley. 

We live on the east side of Denver and never drive to the start of a bike ride. Within minutes I can access a bike trail that connects to a wide network of interconnecting bike trails that travel throughout the metro area. You could easily ride 100 miles or more on a ride from hilly to flat in any direction.

If you want a mountain ride, you could also head west on bike routes or trails and eventually get into the foothills. But it would be a long ride!

You can also easily get on roads that follow Denver's (and the surrounding suburbs) designated bike routes). We've often ridden all the way to downtown Denver through beautiful historic residential neighborhoods. Lots of low traffic and quiet roads.

We can also ride east or south of town and get onto more "country" roads. Maybe not like what's found around Rifle so you're fortunate to be able to live in that area. Denver is a huge metropolitan area so it takes some time to get to more ranch or farm land. But it can be done. 

So we like Denver for riding!

I'm about 50%. I've ridden the roads from my house (between Baltimore and DC) so many times, I get bored and throw the bike on the car and do a group ride occasionally or a rail trail/C&O Canal Towpath ride or a variety of favorite rides that some redeeming quality, like covered bridges or scenic river views etc.

You may be spoiled, but so are we!  

We’re like many others.  We’ve chosen our home location based on access to great cycling roads.  We always ride out of our garage.  We can go in any of 6 directions and within 2 minutes we’ll be out of town and on low-traffic roads.    The ride possibilities have kept us happy for 7 years and I don’t see that changing.

The only exception is when I want to do something stupid like climb some famous col.  In that case, we drive.  :)

We never bike from home any more.  Not surprising, since we don’t have a home any more.

We are in the same situation as you and Rachel but when we are not touring and go back "home" to South Africa we choose our AirBnB/Booking.com accommodation based on how easy it is to find nice cycling out the front door.

Living just west of DC (Vienna), we bought a house 1/4 mile from the W&OD trail on purpose. Probably 90% of my rides start from the end of the driveway and go west on an out-and-back. 

But when I want to do hills, I'll drive out west and just do successive rides "up the hill" (a couple of miles from Leesburg up Clarke's Gap) on the trail, then fly back down on the local roads, only to turn around and do it a few more times.

My daughter lives in Vienna, not far from where the W&OD crosses Hunters Mill Road. I often ride from my house in MD onto the Rock Creek/Capital Crescent trails and then over the Key Bridge to the VA trails to get to her house.

Other times I'll throw the bike on the car, drive to her house and bike west on the W&OD. Somewhere near Leesburg, I'll get off the trail, head south and there is some road that leads to a straight up hill climb and a great view - I forget the name of the road, seems very popular with triathletes and local cyclists.

In the interest of full disclosure I will amend my initial response to add that I sometimes drive to a friend's house a dozen miles away, then ride from there.  He's legally blind and riding on his own is risky, so I am happy to oblige by going to him rather than making him come to me on the Metro or having his wife drive him to my house.