More rat info: A couple of the things they can carry are Rat Typhus/also called Murine Typhus; Plague (there are several forms - it may attack skin or especially the lungs, Pneumonic Plague - Bubonic Plague is when the lymph glands are infected, swell and turn purple, and eventually burst open); and even Hantavirus.

There are others, but those have been found in San Bern. County Vector Control trapping.
The fleas transmit disease even if the rats are dead and gone.First: take in pet food when the pet is not eating. Any feeder that the pet can get food out of, the rats can get food out of - they are really clever. They can fit through any opening that their head can go through - that is, a diameter a little smaller than a quarter. Second, though not so much at this season: take in any fruit that falls off trees in your yard. Keep an eye on bird feeders - might want to take those in at night. Third - trim tree branches and leaves so they don't touch the roof. Ideally the branches would be at least 3 feet from the roof, or any fencing, and not overhanging them - rats can jump that far or drop from overhangs. But in Wrightwood, where houses and trees are dense, I know that would be tough for many. It might be worth putting metal no-climb bands around tree trunks if you can see them using a particular tree.
Go around the house and yard and search for those little openings into sheltered places where they could nest. A clue might be a dark streak on paint or masonry surfaces - their fur is greasy (!) and it leaves grease streaks where they run through most often. Watch especially for those streaks near openings or cracks. Those are good places to set traps. And about bait - just use something firm in texture. Peanut butter is great stuff, but if used alone they will just lick it off without setting off the trigger. Crackers, nuts or fruit slices are good if firmly pushed on or wired on.
Wear gloves for sure if handling a trap with a live rat in it. Transporting further than 500 feet, or about a tenth of a mile, and releasing them is indeed illegal in California. Those who have the nerve to do the rats in would be doing the world a service, but it does take nerve. I'd say try and get the kind of traps with toothed spring jaws that do an instant guillotine action - the animal dies instantly and doesn't suffer, and in some brands the corpse is enclosed in a box so you don't see it. Be sure and spray pesticide around the trap area afterwards, and even more if cleaning up a nest, so that fleas and eggs all die.
If allowed to get densely populated with rats, a neighborhood is more likely to contain diseased rats - so the catch-and-release is not doing anyone a favor. They know that living near man's habitats is much easier than roughing it in the wild, so they will just come back to houses. Call in an experienced neighbor, or a professional, if necessary. More info from the County is available from the Vector Control Program, phone 909-388-4600 or at 800-44-ABATE. They rent traps, and can send out techs to an area to help identify rat hideouts or areas that need repair/cleanout. If nothing else they have pamphlets and info on disease transmission and findings.