Looking to move to northern CA
Maybe Livermore (thought not much more affordable) or Oakley/Brentwood/Discovery Bay/Byron? I don't know what traffic is like on Vasco Road during commute times. You could also look in areas of Fremont, Milpitas, or Northern San Jose, which would be a reverse commute to that area. It would be more affordable but is not nearly as nice. I used to commute from Fremont to San Ramon every day, and it was not bad, but I didn't have kids at the time so I don't know about schools in that area.
Have you considered moving a little further away than 20 minutes? Tracy is a lot less expensive than anywhere near Dublin, San Ramon, Concord, etc. Tracy is between 30 - 45 minutes away from Dublin/Pleasanton/San Ramon. Depending on what time of day you are needing to commute, your driving time could be even less. I've made it from Manteca (where I live and is further away from Dublin than Tracy) to San Leandro (which is about 15 minutes closer to the East Bay area) in 45 minutes instead of an hour during non normal commute hours.
Wanting the DS!
If you care enough for the result, you will almost always attain it. - William James