We lived in Winchester for 15 years (just recently moved to NM). Raised our kids there in the same house. They went to school in the Menifee district. I have never seen a 'squatter' in all the time I've lived there. The 'vagrants' I've seen were in Temecula in the area across from the post office and down the river along Jefferson.
The pro's (IMO) are: large-ish parcels of land available. Big sky. Close to shopping but far enough away not to be right in your face. I drove to Hemet for the Henry's market, and to Menifee Ralphs shopping center for the Target and a great Mexican Food restaraunt (Casa Viejo). Diamond Valley Reservoir for recreation. Fresh yummy strawberry stands everywhere when it's the picking season. DO take advantage of this, you can get a flat of 4 baskets for like $8.00 and they are all ripe.
Now I'm missing strawberries!
The cons (IMO): gets REALLY cold in the winter and REALLY hot in the summer. Not much protection from the elements (that 'big sky' I mentioned). Leon floods at Scott Road every year. That's the lowest point and it all drains there and stays wet. It also floods at the College (San Jacinto) frontage road. If you are going to be rural prepare yourself for the rainy season. There WILL be mud
There are housing tracks on the Temecula side, around French Valley area. But the traffic starts to get nasty there in the mornings and afternoons. Also new houses on the Menifee side. Both are real nice, and not so 'rural' if you don't go for that.
Enjoy Winchester!