Oooh...we are in the same boat too :)
As far as public primary school here in CA (and the whole US), you are provided with a free, public education based on your home address. So, once you've decided where to live, you would contact the local board of education office and then begin the registering process there--no matter what time of year.
For school reviews you need to go to greatschools.org, I think that you have to read over all the reviews, especially the community reviews.
I was recommended Mountain View School and Palo Alto as excellent areas but again - it's a matter of research!
With any public school system, once you've signed a lease or closed on purchasing a home, and have all the correct documents, you can call their board of education office and make an appointment to register--any time of year.
I think rents in California are close to London prices!! Let me know how you get on with your research - where will hubby be based? It would be wise to look round there as a starting point and see about affordability.