Unfortunately, no. California ocean fishing regulations prohibit any person from having more fish in their possession than is prescribed, even if they were taken from different sides of the border. Once you cross the border, you must complete a Declaration for Entry form listing all fish taken in Mexico, and offload your catch without fishing along the way. The form is available on page 79 of the 2010-2011 Ocean Sport Fishing regulations booklet or online at www.dfg.ca.gov/enforcement. If you do stop to fish on the U.S. side, all fish in your possession must then meet California regulations, which are often even more restrictive than those prescribed under the laws of Mexico.