If this firm says they haven't decided if they'll take the case, and there's no signed fee agreement, it sounds as if there isn't any lawyer-client relationship yet. Best advice would be to tell them you're going to contact other firms, and thank you very much. Two months to decide whether or not to take a case is plenty. Unfortunatley, this won't necessarily expedite your case as you will now need to contact other firms who will then weigh whether or not to take your case. However, many firms make such decisions on the spot.
The determination regarding whether or not you are entitled to overtime from your employer is a relatively simple one. If you are a non-exempt employee, you are entitled to any time that you work more than 8 hours a day, or 40 hours a week. In deciding whether or not to take your case on contingency, a lawyer may consider the number of employees who didn't receive overtime pay and financial viability of your employer. If you have yet to sign a contract regarding representation, I would encourage you to seek other representation from an experienced California employment attorney who is well versed in overtime law.
This answer is for informational purposes only and does not create an attorney/client relationship.