Have climbed a number of these now after a brief time spent living in the IE. Great for a weekend afternoon or weekday jaunt when higher elevations are snowed in. It's my understanding that most of these mountains originally had denser vegetation (manzanita, for example), but over-frequent burns have now left mostly fire-resistant species - especially bunchgrass.
I stayed in Fontana for about a week in April 2015 and enjoyed the prevalence of small mountains in the area. I hiked up Mt. Jurupa twice. The second time I bushwhacked down the west slopes to also climb Peak 1802, which has some nice boulders on the summit as well as a surprising amount of vegetation. I also hiked up a 1,602-foot peak not far to the east of Jurupa, called Rattlesnake Mountain on old topo maps. It was unremarkable, but I climbed it for its name. Slightly more interesting were Peak 1452 to the southeast of Rattlesnake Mountain, and Peak 1739 to the south. More recently I hiked up Peak 1913, just east of Mt. Jurupa.