Africanized Honey Bees (AHB), also called "Killer Bees" by the media and horror movies, are a hybrid species of bee that is generally more defensive than the common European honey bee (EHB). They might be more visible than other bees, since they tend to form smaller swarms more often than EHBs, and build hives in smaller places, such as water meter boxes.
Since 1999 all feral (wild) bees in Los Angeles County are considered "africanized". This is not a reason to panic when seeing a bee, but a reminder to treat all bees with respect and leave them alone. While bees are out foraging and pollinating flowers, they focus on their task and will usually not sting somebody unless provoked.
For information about local honey bees check out www.avbeekeepers.com