East Palo Alto
While Palo Alto is considered one of the more affluent areas of Northern California, East Palo Alto has a less posh reputation. In the early 90s it had one of the highest murder per capita rates in the USA, though that has changed in recent years (article).
Fireworks are illegal in East Palo Alto, but there is a grand tradition of celebrating with them, especially on New Year's and the Fourth of July. It can be one of the best places for fireworks in the Bay Area.
The population of East Palo Alto is largely Latino and there are some fantastic restaurants from those cultures to try including the Three Brothers Restaurant on University and Taqueria La Cazuela on Clarke.
East Palo Alto has historically been known as one of the more dangerous cities in the Bay Area, though this has changed in the last decade (article).