You have two issues here.
First of all, communication between the parents have nothing to do with what they speak to the children. My own grandmother never learned her parents' Russian because they were part of the immigrant generation who thought that would be damaging. We know now that to be a myth but communication between adult parents has little, if any, impact on the child.
So are you debating between both of you speaking Spanish to her or doing OPOL? Speaking a non-native language to your child, especially outside of the country, is not often so easy. It's a personal choice and you can switch later on, especially to the community language.
We do OPOL and I will admit that this is not the best method. I speak English to my kids in France. Their exposure to French is so much more than that to English, since it's basically just me. All are fluent in English though so OPOL works for sure, but it's not an even balance.
Please though, choose a language and stick with it. Resist repeating everything in both languages (the kids "tune out" the weaker language anyway) which is headache-inducing for you too!
Just because you want to interact with your dd in both languages doesn't mean you have to do it from the get-go. You can let her get a good grip of both before mixing them up. Children are rigid because they want to relate to those in their lives in just one language. If you mix them from the start, it's very likely that since you all live in the U.S., she'll just decide that her stronger language, English, is what she wants to use with you.
You can see plenty of children in California who can only understand Spanish but can't speak it. The advantage of learning a language young is that they can pick it up without an accent. By answering back in their easier language (English), they don't learn this and abandon the more difficult skill-speaking. The result is that they never achieve full fluency in Spanish.
A big price to pay just because the mother wanted to mix both languages from the start!
When my children got older, we did end up using some French terms. My kids did pony riding and gymnastics. I don't honestly know a lot of the terms in English (saddle but then what is the padded thing underneath?) School supplies? There is a different term for each kind of notebook. We just give up and use the French lol! But my children have a firmly-established relationship with me in English, the only reason why they are truly bilingual.
Since you're in L.A., you should have an easier time with the Spanish (I'm in a part of French where NO ONE speaks English). You may want to look into bilingual schooling. This would support your husband's efforts and also later on give her the academic foundation in both languages.
No, it's not too early to look into these schools. Many have waiting lists and you may want to select now, in case you move (which many young families do) to place yourselves closer to your choice.
From what I've heard, it's easier to get into a bilingual school as a native Spanish speaker so this might be inspiration to use Spanish with her, at least at first.
Dual "immersion" is best. This is where half the class are native Spanish speakers and the other half speak English as their first language. My kids are in a bilingual program but it's designed for native French speakers to learn German. There are native German speakers in the class but they had to be fluent in French to start it (a requirement) and quite frankly, the level of German is easy for them. British friends here in France thought their son would do better in a bilingual school but the kids were mostly French speakers so their son found the English too easy and the French too hard. So not all bilingual classes are the same!
The methods that you're debating between are OPOL and "home vs. community" in case you read up on the subject. Look on the Amazon list because they have a good collection of bilingual parenting books. You don't have to buy any from them but it's a good source of reviews.