Those look like nice trails but personally I think there are many better options. I get that the emphasis is on trails that are not in or near cities but it is nice when top quality bike trails are where the people are. For example, the Discovery Trail on the Long Beach Peninsula sounds nice and I admit that I have not ridden it (even though I live in Seattle not too far away), but it is not convenient for many people - a bit off the beaten path - and is only 8.5 miles long. I am sure it is nice way to spend a leisurely hour, or a little more.

Alternatively, in Portland, which you mentioned, there is a wonderful network of trails, many in very scenic areas around the city and separated from auto traffic. Riding in the heart of town on the separated paths along the river is a blast as well.

I just returned from three nights in Boston which my wife and I visited for the first time. We took the Bromptons and rode the Freedom Trail, visiting 15 or 16 of those famous historical site we all learned about in elementary school. Then we rode up the north side of the Charles River on the bike trail past MIT, Harvard and Cambridge and crossed over to return on the south side. It was a delight to see people out in small sailboats, kayaks and rowing shells on the water or jogging, cycling, strolling and picnicking along the shore. The next day we rode along the Harborfront Trail. There were quite a few routes through town that had well delineated bike lanes.

But I understand your lament. We are fortunate in Seattle to have the Burke Gilman Trail and Sammamish River Trail, among many others, that utilize old railroad right-of-ways. Personally my priority is for improvements in and near the population centers, which is a different focus from the article that was linked.

Will it happen in Arizona? Well, you alluded to a political climate there where perhaps the majority do not see value in providing public amenities that can be enjoyed by all. As for rain in Portland - once you settle in it will not limit you - it is not as bad as you may believe - and worth the trade-off to not have to live in the AC. Come on up!