This is a cool trail. It just sucks that it has to be interrupted by major streets once a while but when you press the crosswalk button, it responds quickly. I rode my bike, walked, and jogged on this trail. I do agree that going towards downtown Manteca is a little sketchy but on this trail you'll pass a baseball field, a skate park, the library, and towards the end you'll find yourself close to Target. I'll usually continue off the trail to go towards the newer apartments and go by another huge park in Manteca. All in all, good paved roads, no trash, and people are generally polite.
This trail has drinking fountains along the route so running it during the summer is a little more bearable. It's asphalt, but the grounds are well maintained. The city does a good job of covering up the graffiti that's been painted on the path. It's somewhat dodgy towards the center of town; bums pushing carts around, the aroma of urine, and the occasional shoddy drug deal going down on a bench, so I try to stay out of that area. All in all, if you're a runner trying to get mileage in this is a good place to start.