Yes, with conditions
1. What the city publishes
Gold panning and metal detecting may continue within the boundaries of Fain Park, so long as such activity is limited to – a. use of gold pans, metal detectors, and hand tools such as picks and shovels [use of motorized or mechanical equipment or mining aids … is prohibited]; b. excavations made below the high water mark of the stream channel that do not damage or disturb root systems of live vegetation and are filled in before the [end of the activity]
Source: codelibrary.amlegal.com/codes/prescottvalleyaz/latest/prescottvalley_a
2. The state rule also applies
Arizona State Parks does not allow it, as published policy. There is no regulation behind that – the state's park rules contain no metal detecting provision at all.
3. County rules
Awaiting review.