As I'm sure you are well aware, a fourth DUI within a ten year period is a felony. The maximum sentence for a felony DUI without injury is up to 3 three years. Prison is not mandatory and a lot will depend on your individual circumstances. How familiar with Tulare County are you? I practice in Tulare County and they have quite the reputation for being tough on crime and handing out harsh sentences. The fact that you were on probation for DUI is not good. This does not mean that an attorney can't help you though.
Have you already pled guilty to the fourth DUI? If not, you and your attorney need to focus on how to beat it. Why were you pulled over? What was your blood alcohol content?