The Maricopa County Sheriffs Office which provides law enforcement services to Sun City is on the Maricopa County trunked system. You'll want the White Tanks site. It won't hurt to also include the Phoenix Simulcast, and maybe even the Thompson Peak site, particularly if you also want to hear deputies at Lake Pleasant on the Lakes talkgroups.
Sun City is part of District 3, the Northwest Valley. (Roughly west of I-17 and north of Northern Ave.) You'll mainly want the District 3 talkgroup, although most of the time, District 2 and District 3 are multi-selected, and you'll hear the same transmissions on either talkgroup. (District 2 is the Southwest Valley, roughly west of I-17 and south of Northern Ave.)
341, 342, and 343 are the primary deputy callsigns that patrol Sun City. The alpha prefix denotes the shift and whether a single or two deputy unit.
You'll also want to listen to 158.910 car-to-car, 159.090 "Search 8", and 159.390 Lake Pleasant car-to-car.
John
Peoria