I've been living in San Pedro for a few years now and have been looking for great Mexican food without much luck -- growing up in the East LA area with great family cooks has spoiled me for good. However this past weekend I found a taco truck in Harbor City that was excellent.
Its called Tacos El Gallito and its on PCH just west of the 110 in Harbor City. Carne asada was good (not gristley with a good flavor) and I especially liked their al pastor -- very fresh tasting and not too greasy. They have a heavy hand with the onions and cilantro, so be sure to specify your liking when you place an order. Their salsa verde tasted fresh and flavorful, and even the horchata was pretty good. They also offer roasted jalapeños on request which is a big plus in my book.