"To make things worse, this beast appeared to be a Pit Bull. "
There is a beast of a Pit Bull that chases me every time I come home from a ride also. Oh yeah, that's my dog.
Seriously, I work in Rancho and my parents live there. I sometimes ride from their house after work in the area you are referring to and sometimes I will ride to Lytle Creek from my house in San Dimas. That area used to be way worse when I first started riding in the late eighties. There were less cars but every house up there had loose dogs. If you didn't feel like sprinting, the water bottles wouldn't work. You would have to take off your frame pump and hit them over the head.