I know the park well, on the N. side of Indian School road between Central and 7th street, before it was the park it was an actual school for American Indian's and the road it is on was named named for it.
I have lived in the Phoenix area for 4+ decades and much has changed in that time.
What hasn't changed is rust is not natural in this climate, in fact you have to show a great deal of neglect and irresponsibility to get rust on anything.
That is not to say some things don't look better being 'rustic looking' like this 49cc 4-stroke Felt MP I built for a customer that wanted Korea War era rustic.
Around here we delight in keeping everything shiny and new looking for decades especially things like bikes and cars.
Take this 1990 Pontiac Grand Am LE with 135K I recently inherited when my pops passed a couple of months ago...
It still runs like a top, no oxidation and darn sure not a spec of rust anywhere just the way we like it here.
Hey FP, maybe we'll run into each other some time and if you ever want a little motor assist on your bike I'm your guy and just north of you in Sunnyslope, been doing custom builds here since 2009 with about 100 under my belt, you see many here
http://KCsBikes.com