In-custody time instead of work release?

I was recently fighting a case in one county and another case in a different county. Both cases I plead guilty. I was sentenced to 120 days work release in one county and 30 days work release in the other. This means I have to do work release 4 days out of the week because I have to do 2 days a week for each county and they can't be on the same days. That would only leave me 3 days to go to work. My employer wouldn't be happy with that type of inconvinient schedual...but that's not a problem anymore because they fired me for missing so much work already due to all my court hearings. Now I can't even afford to pay the fee to sign up for the work release. I'm over it. I would rather serve my sentences in jail now. And I don't really have much of achoice anyway I guess. So can someone tell me how to go about asking for the in-custody time instead of the work release? Do I talk to my probation officer or go put myself on calendar and ask the judge or what? Anyone that can let me know, ide appreciate it a lot. Thanks. (I live in california also..if that's important)