When your child's school presents you with an IEP document after an IEP meeting it is up to decide to consent to it. You can refuse to consent to the whole IEP. You can also consent to only parts of the IEP. For example, if after an IEP meeting you are given an IEP document which reduces the amount of speech your child was receiving, and adds an accomodation for test taking, you can agree to the accomodation, but not the reduction of speech hours.
Be careful how you communicate your consent to the IEP. If you simply sign the IEP indicating you are in agreement with it, you have agreed to all the changes. If you want to accept one thing but not the other, you have to make your intentions clear. If it is possible, and space permits, you can simply write on the signature page the parts you are agreeing to and the parts you are not. You could write for example, "I agree to the whole IEP, except I do not consent to the reduction of hours of speech therapy". You can also refuse to sign on the dotted line at all, and instead send a letter spelling out what you do and do not consent to.
Schools have a duty to implement that parts of an IEP that a parent has consented to. So, a school district would be violating Section 56346(e) of the California Education Code and the IDEA (34 C.F.R. 300.300(d)(3)) if they were to refuse to provide the accomodation in the IEP because you did not consent to the reduction in speech hours. Beware however, sometimes schools will claim that they cannot deliver the portions of the IEP consented to, due to certain other parts being refused. For example, if you refused to allow your child to be placed in a special day class, a school may argue that they cannot implement certain accomodations that are only available in a special day class.