HELP PLEASE!!! URGENT! Is it illegal or legal to have a big party in your front yard?

I would let all the neighbors know, that includes the neighbors behind your house. Yet you may also want to check with your local city hall. I too live in so cal and they require a permit in my city to hold a yard sale. But either way let your neighbors know and give them your phone number so they can call you first if it gets loud. Lastly, I went to a poker tournament in my friends uncle's backyard, he has the same issues with the dog so they rented carpets from a party rental place and covered up the whole backyard for the night, it was quite nice actually. If you have the means to do so check that option out.