Del Balgas is a great midwife and I believe she just opened an office for seeing patients in Orange. She's been around for a while and I've worked with her on a couple of occasions.
I wouldn't worry so much about a "backup doctor" so much as having good support in the home birth you would like. If an emergency arises, it's an emergency and it really doesn't matter who the "backup doctor" is. A home birth midwife will see you through all of your prenatal care and they should legally have a supervising physician (but the physician doesn't even need to be in California, just licensed here).
If you haven't yet thought about having a doula, you should consider it. Here's my website in case you're interested: www.yourlovingbirth.com but there are lots of highly qualified doulas in the area.
Also, because you have had a miscarriage you may want to think about how you have dealt with your loss. In many cases a birthing mom will have trouble progressing in labor due to the trauma (emotional or physical) that occurred previously. If you properly deal with this trauma your labor will probably go much smoother.
Unfortunately many moms don't have a very discerning eye when it comes to OBs. If they come across as "nice" or well educated or any other positive quality, most moms will call their OB an awesome doctor. Most, however, are not very good at allowing a mom to birth the way she was meant to. They are there to rescue in an emergency, and 99% of the time, they forget that. Instead, they direct a labor and unfortunately that direction often leads to a surgical birth. More interventions=higher RISK!
BJ is an amazing midwife, teaches midwifery and nursing at a local university and actually has her doctorate in nursing. She runs a beautiful birth center in Laguna called Beach Cities Midwifery and has an amazing staff. If you want a birth center birth, that's definitely a way to go. There is also one in Irvine but I'm not very familiar with it, it's called South Coast Midwifery.
Congratulations on your pregnancy! I hope things go well and you achieve the birth you desire. Let me know if you have any questions.