Emily, Tucson doesn't have the air inversions Phoenix has, unless something has changed, although the risk of Valley Fever is still the same. Almost everyone who lives in the southwest has had Valley Fever, although most do not know it. I didn't know I had it, until 2005, when I went for a CT scan for something else and some "spots" showed up on my lungs. My PCP freaked and sent me to a pulmonary doctor, who thankfully, looked at me when I walked into his office and said, "Where did you live in Arizona?" But I have to explain this every time I have an x ray, as x ray techs, etc. do not know what they are looking at. I pretty much can guess which one of my bronchial illnesses was Valley Fever, and truly, I haven't been the same since.
I would still visit Tucson for a couple of months, but be mindful of any bad air alerts, use a humidifier, and avoid exercising very early in the AM in the winter.