If you see signs for a DUI (sobriety) checkpoint YES you may avoid the checkpoint by legally making a left-turn onto another street or if allowed you may turn around (u-turn). The case where this was determined is Ingersoll v. Palmer, 43 Cal. 3d 1321.
The court in that case said that if you see a "sign announcing the checkpoint" a motorist is allowed "to turn aside, and under the operation guidelines no motorist was to be stopped merely for choosing to avoid the checkpoint." Id. at 1327. The police cannot pull you over (detain) without you first breaking the law. If a police officer detains you without cause than the case can be dismissed.