My husband and I went through this process in 2011, so I'm not sure if my info is out of date or not, but I can give you an idea of our experience...
I (USC) went back to the US to file the marriage visit visa in February of 2011. We took a little while getting our documents together (long story about deciding where to live on the back of a denied US visa), but we ended up filing sometime around the beginning of March 2011.
I'm not sure if I'm remembering correctly, but I think you fill out an online application first, then you print this off and mail it along with your supporting documents. From what I remember, once you submit the online application, they give you instructions to apply for a biometrics permit, which you then print off and take to your appointment. I did have to wait a couple of weeks for an appointment, but sometimes you can get an earlier one at a different centre, it just has to be in your state of residence. For instance, your wife is in Sacramento, but if she can get a quicker appointment in LA, she might as well make the drive to save time.
We did the priority service and it came back really quick once we sent the completed application off. I think the whole process from start to finish was only about 4 weeks. It's a really straightforward process, so don't worry. Best wishes for your wedding.