Some Euphorbia should do well. Also, what about Sedum and Yucca? It would be interesting to try some of the hardier Agave as well.

Another one to consider is Echinacea, and possibly others from the Aster family, e.g. Heliopsis, Silphium, maybe Eupatorium (unless it's too dry), etc.

Kniphofia are pretty tolerant of a wide range of soil conditions, so not sure you can make any hard and fast assumptions as to what your specific soil may be like just based on them. They DO need good drainage however, else liable to crown rot, so that may be one reasonable assumption.

There are various home tests you can do to help understand your soils.
1) Testing for soil texture
2) Percolation/drainage test
3) pH test. This does require the purchase of a home pH test kit, available at most home improvement stores and garden centers. They are quite inexpensive - around $5 or so - and perhaps the most accurate of any of the home testing kits. But be sure to use distilled water as the testing liquid - regular tap water will skew results.

And I'd encourage you to rethink your priorities with regards to the soil. The soil quality is the foundation for any successful garden and any time, effort or expense you devote to it is an important investment. It is far better to spend some bucks and some time in improving your soil before you plant than to waste money on unsuccessful plantings simply because your soil quality is not adequate. Many new gardeners make this rather unfortunate and hard to correct after-the-fact mistake.

Also, because of your location in a pretty arid climate, I'd look into drought tolerant/xeric plants. Once established, these will need minimal attention in terms of watering and are often happy in lean or less than fertile soils. Many of those mentioned above would work provided your soil is suitable. High Country Gardens is an excellent resource for these types of plants.

Here is a link that might be useful: High Country Gardens

When many see Arizona they think desert but much of AZ isn't desert. :)

ZONE 2B: Warmer-summer intermountain climate

This is a zone that offers a good balance of long,warm summers and chilly winters,making it an excellent climate zone for commercial fruit growing. That's why you'll find orchards in this zone in almost every state in the West.You'll also find this warm-summer, snowy-winter climate along Colorado's Western Slope and mild parts of the Front Range; in Nevada from Reno to Fallon, then north to Lovelock; in large areas of northern Arizona and New Mexico; and in mild parts of the Columbia and Snake River basins. Winter temperatures are milder than in neighboring Zone 2a, minimums averaging from 12 to 22*F (-11 to -6*C),with extremes in the -10 to -20*F (-23 to -29*C) range. The growing season here in Zone 2b runs from 115 days in higher elevations and more northerly areas to more than 160 days in southeastern Colorado.

Thanks cooolplantsguy and gardengal48! I'll check into your suggestions.