Can a defendant appeal from a judgment of conviction upon a no contest plea?

Defendant contends section 1237.5 allows him to appeal from a judgment of conviction upon a no contest plea where he has shown "reasonable constitutional, jurisdictional, or other grounds going to the legality of the proceedings" and the trial court has issued a certificate of probable cause for such appeal. ( 1237.5, subd. (a).) He claims that, because the state had no right to consolidate the amounts stolen so as to charge him with felony grand theft, his plea was a "legally impossible admission," which questions the legality of the proceedings and thus may be challenged on appeal. As support for this claim, defendant cites People v. Soriano (1992) 4 Cal.App.4th 781, 783 (Soriano).