I am sure Blue is correct - Petitions for legislative or law changes require the signatures of registered voters in the state where the change will be on the ballot or considered by the legislature.
Getting signatures from folks not in California will only slow the process because the majority of the signatures will be thrown out as invalid.
You might contact pet stores - especially chains like Petco and Petsmart to see if they would circulate the petition, post the link for the on line petition or allow someone to collect signatures outside the store.