In order of the ones I'd go to (and, I've been to them all):
1. Cabazon (Palm Springs)--avoid next door casino at all costs, but the two, neighboring outlet malls are good.
2. Camarillo, smaller than Cabazon, much better weather, apparently is within some sort of retailing exclusion zone for being too close to L.A. to have many of the very fanciest outlets.
3. Ontario: skip it.