Of course they can override the veto with a 2/3rds majority in both houses.
Democrats do not enjoy a 2/3rds majority in either house of the California legilsture.
The Democrat's lack of a 2/3rds majority is the primary reason Schwarzenegger has struggled to get his proposed budgets and bonding measures approved by the California legislature. Most Republicans have refused to go along with his liberal promotions. Schwarzenegger and his Democrat allies have had to pick off Republicans, one at a time, to meet the super majority requirements.