What kind of plants will keep the neighbor's cats away from my garden?

Spread moth balls. Cats hate the smell.

Buy one of those motion-detector cat deterrants you attach your hose too, and train kitty to stay away... https://www.amazon.com/s/ref=nb_sb_ss_i_5_13?url=search-alias%3Daps&field-keywords=cat+deterrent+devices&sprefix=cat+deterrent%2Caps%2C212&crid=LT9TD2P4YAPC

Thanks for your information, I bought the moth balls already.

Cats prefer to walk on soft soil and will avoid prickly surfaces. Cover the garden in twigs, or placed a couple of inches apart throughout the bed push pine cones or other prickly yard trimmings down into the soil around your plants.

They also dislike the smell of rue, lavender, pennyroyal, coleus canina and lemon thyme, inter-planting will attract pollinators and can help to avoid pests too.

Strong citrus scents are also a deterrent, throw citrus peels directly on the garden.

Cats hate the scent of human hair, empty your brushes onto the garden. (Stay away from moth balls though — this is a commonly cited suggestion — they are toxic to cats & humans).

Mix up a batch of cat-away spray. Combine 1 tsp of black pepper, dry mustard & cinnamon in a spray bottle with a few drops of citrus essential oil and a crushed garlic clove. Fill to the top with water. Leave out in a warm, sunny spot for 24 hours before using. Do not refrigerate. Apply to your garden beds. This magic combination of strong scents is an unparalleled kitty repellent.

Best of luck to you... as they say, been there - done that! Cat poo can be harmful to humans, so we want to keep them away from our bountiful harvest!

Keep sprinkling White Pepper around the garden. Plain and simple. They will eventually get the idea and go elsewhere. I know this works!!!