The San Jose Police Department was out in full force Sunday, and will continue Monday, making sure Cinco de Mayo is a peaceful celebration.
Celebrations in the past, like in 2007, have led to violence and vandalism, so more officers were out on the streets, police said. There were also more CHP officers patrolling the highways.
On Monday, police reported they arrested 21 people on Sunday, compared to 12 last year.
San Jose police were working traffic control Sunday at Story and King roads, as well as at Fourth and Santa Clara streets. For much of Sunday afternoon and evening, some streets, including Santa Clara Street near City Hall, were shut down in San Jose just before the official start of Cinco de Mayo Monday.
Police reopened the streets late Sunday night but said they are prepared for more crowds Monday.
Officers said they were looking for drivers who may have had too much to drink and get behind the wheel.
The Santa Clara County Sheriff's Office also said it had its gang task force out this weekend too.
On Sunday, an unlawful crowd was ordered to disperse at 19th and Santa Clara streets, according to police. At least one arrest has been reported.
A source told NBC Bay Area certain deputies were looking for parole or probation violators--people who might be the source of problems.