The vandalism was reported at about 2:35 p.m. by a witness who said two men were spray-painting graffiti onto the cement wall directly below his backyard.
Arriving officers contacted Richard Holmes, a 19-year-old Redwood City man, and Scott Doolin, an 18-year-old Menlo Park man, as the two men exited the area near the creek bed and took them into custody.
Both subjects had paint on their hands and clothing and were in possession of a backpack full of spray paint cans, according to police.
A search of the area found graffiti "tags" on two walls, and a police investigation indicates the suspects are responsible for at least eight separate incidents of felony vandalism in San Carlos.
The graffiti tags are well-known to San Carlos police and other agencies in San Mateo County, and the investigation will continue to determine the total number of vandalism incidents in the area.
The vandalism so far has caused damages of more than $50,000, police said.
Holmes and Doolin were booked into the San Mateo County Jail on multiple charges of felony vandalism and criminal conspiracy, police said.