There were several engagements of note between the Californio's and the invading Americans. The one you're thinking of is the Battle of San Pasqual, which indeed is near the San Diego Wild Animal Park. Californio's met two companies of US Dragoons under General Stephen Watts Kearney, who had just marched from Ft. Leavenworth, KS by way of Santa Fe, to take the reins of the new territorial government from Commodore Robert Field Stockton USN and Captain John Charles Fremont, USA. Their claims to have totally suppressed any unrest in California, carried east by Kit Carson, were somewhat overstated. The interesting part of this engagement was that most of the wounds received by the Dragoons were lance wounds to the buttocks, which more suggests that the Californio's were more interested in embarrassing and discomfiting the invading Americans than in killing them. Only one American was shot, that was Captain Johnson who's thoroughbred horse outdistanced his Dragoon's worn troop horses in their initial charge. He was shot in the forehead by the only Californio present with a pistol (who was considered somewhat eccentric by his fellows because he carried a pistol, and liked to shoot it too.)
The other engagements were:
The Battle of Los Angeles, which took place on the plains between LA and San Pedro, which the US Navy still held securely. After the 11 or so Marines had been ejected from Los Angeles by the Californio's who were upset at the new regulations forbidding them to hold fandango's, Captain Mervine of USS Levant sent a force of sailors and Marines to recapture it. Unfortunately Mervine forgot to send any artillery support with them, which the Californio's had dug up an old cannon that had been buried in an old lady's garden, thus "The Battle of the Old Woman's Gun".
The Battle of San Gabriel, where the combined forces of Stockton and Kearney marched north from San Diego (after Stockton's sailors and Marines had rescued Kearney from Mule Hill) to retake Los Angeles, this time from the east side. The Californio's had attempted to stop the American forces from crossing the San Gabriel river by emplacing two artillery pieces at strategic points near the crossing. Stockton, being a skilled gunnery officer and developer of such things (and being somewhat smarter than Mervine), had one of his pieces dragged forward, aimed the piece himself and shattered the Californio's gun carriage with the first shot. That was pretty much the battle. The Americans surged across the river (such as it was in January of 1847) and continued on.
The Battle of La Mesa, which took place the following day, saw the US Forces forming square to fight off the mounted Californio's, who charged them several times. Between the much superior firepower of the Americans, and the inability of the Californio's to close due to the use of boarding pikes by the American sailors, the Californo's withdrew and the way to Los Angeles was open.
That's about the size of it for the War in California, but it was a whole lot more interesting than most folks realize. There are a LOT of very cool aspects to the March on Los Angeles by Stockton and Kearney, especially insofar as the small-arms issued to the Marines, Sailors and Dragoons, but that's for another time. Suffice it to say that the force was armed and equipped with both the most modern, and the most ancient of weapons for that particular campaign.
Cheers,
Gordon