Just an update: It is no longer necessary to turn south on the 57 fwy at Glendora to access the 10 freeway in Pomona (unless you intend to stop at the CG in San Dimas mentioned above). The 210 (called the I-30 east of the 57) has been opened now all the way through San Bernardino where it joins the I-10 in Redlands. This is, by far, the best way to avoid E/B I-10 traffic which can get pretty bad around the 57 interchange and east through Ontario in the afternoon.
The 210, back towards LA, is a godsend compared with trying to drive through LA in the afternoon to get to the E/B I-10. Remember, though, it still gets a little backed up for about 10 miles through the Pasadena area to the 57 interchange.
If your going to be on the 10 E/B, remember the Coachella Valley (Palm Springs) area for stopping spots also. There are several great CG's in the valley, ranging from free (there are 3 or 4 casino parking lots off the 10) to pricey. Also some of the best restaurants, shopping and entertainment to be found anywhere. If you do stop in this area between the end of June and about mid October, make sure your A/C units are in good working order!