As I understand it, 484(a) PC in CA is a misdemeanor for petty theft. Even if you get permission from your probation officer to travel, you still could face inadmissibility charges on your way back into the US based on CIMT. My advice, don't travel!
U.S. immigration may give you a problem because any theft, even a misdemeanor, is considered a Crime Involving Moral Turpitude. You should consult with an immigration attorney.
Seth Weinstein, Esq.
Southern California Criminal Defense Attorney
This reply should NOT be considered a legal opinion of your case / inquiry. At this time I do not have sufficient factual/legal documentation to give a complete answer to your question and there may be more to the issues you raised then I have set out in my brief reply.
If this a your only conviction, it falls within the "one petty theft" exception and is not a deportable offense,
(213) 394-4554 x0 Mr. Shusterman is a former INS Trial Attorney (1976-82) with over 35 years of immigration experience. His response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.