You are only entitled to privacy that a reasonable person can expect in your place. The resulting rule of thumb is that one can photo/film whatever private property they can see from public/their place provided that they do not use special equipment (e.g. tele lens) allowing them to see more than a human eye.
If your new neighbors were just standing there where the cameras are and staring at your yard/window, you would have no claim: they can stand there and look wherever they want. However, if they were using a telescope to penetrate through your bedroom window and see you having good time which a reasonable person in your bedroom would not expect anyone to see, that would be a privacy breach.
The mere fact that it is artificial eye (a camera) seeing your yard/window and not neighbors themselves does not mean that your privacy is breached; this is simply equivalent to a person/guard sitting up there 24/7. For a successful breach of privacy claim you need to prove that the camera is able to see more than a human eye.
Applicable California laws:
California Civil Code section 1708.8(b) (emphasis added):
A person is liable for constructive invasion of privacy when the
person attempts to capture, in a manner that is offensive to a
reasonable person, any type of visual image, sound recording, or other
physical impression of the plaintiff engaging in a private, personal,
or familial activity, through the use of any device, regardless of
whether there is a physical trespass, if this image, sound recording,
or other physical impression could not have been achieved without a
trespass unless the device was used.
California Penal Code § 647(j) (emphasis added):
every person who commits any of the following acts is guilty of
disorderly conduct, a misdemeanor:
(j) (1) A person who looks through a hole or opening, into, or
otherwise views, by means of any instrumentality, including, but not
limited to, a periscope, telescope, binoculars, camera, motion picture
camera, camcorder, or mobile phone, the interior of a bedroom,
bathroom, changing room, fitting room, dressing room, or tanning
booth, or the interior of any other area in which the occupant has a
reasonable expectation of privacy, with the intent to invade the
privacy of a person or persons inside. This subdivision does not apply
to those areas of a private business used to count currency or other
negotiable instruments.
(3) (A) A person who uses a concealed camcorder, motion picture
camera, or photographic camera of any type, to secretly videotape,
film, photograph, or record by electronic means, another identifiable
person who may be in a state of full or partial undress, for the
purpose of viewing the body of, or the undergarments worn by, that
other person, without the consent or knowledge of that other person,
in the interior of a bedroom, bathroom, changing room, fitting room,
dressing room, or tanning booth, or the interior of any other area in
which that other person has a reasonable expectation of privacy, with
the intent to invade the privacy of that other person. For the
purposes of this paragraph, “identifiable” means capable of
identification, or capable of being recognized, meaning that someone
could identify or recognize the victim, including the victim herself
or himself. It does not require the victim’s identity to actually be
established.
As one may conclude from the wording of the cited laws, for a successful privacy breach claim you would need to prove that your neighbor actually attempts or intents to invade your privacy — as opposed to merely ensuring their security. Given that the cameras are not concealed or secret, and have a plausible purpose, you would have to collect additional evidence of the neighbors' intentions; merely the fact that the cameras are there is not sufficient proof of a breach of privacy.
