You cannot pay child support in California just by giving your ex cash and telling him or her that it's for a support payment. The law says that everyone in the state who is paying support actually needs to send it to the State Disbursement Unit first, and then it is sent out to those who are to receive it. This makes payments easier to track and verify.
There are advantages to regular alimony payments, such as the fact that they keep you from spending the money too quickly and they provide you with a stable, predictable income for as long as you get them. If you're being paid $3,000 per month, for instance, you can set up your budget to reflect that income level and create a lifestyle that fits your means.