Different states have different laws about whether their courts can rule on the constitutionality of initiatives before the initiatives have been voted on. However, there are definitely states where it is possible for the courts to make such rulings. Therefore, the best answer for this question is “False.”
For example, state courts in California clearly have the right to rule on the constitutionality of proposed initiatives. The courts do not choose to exercise that right very often, but they do have it. The article in the link below gives us evidence of this fact. It tells us that there have been six initiatives or referenda in California that have been reviewed by the courts before being voted on. Of those, three were removed from the ballot. This makes it clear that the courts rarely rule on initiatives, but it also makes clear that they have the power to do so.
Thus, the statement in this question is clearly not true for all states. Therefore, unless the question refers to a specific state, the best answer is “False.”