I think that confidence intervals are beyond what is intended in the standard S-IC4. Students should have an idea of what margin of error is and how it is interpreted, which can lead informally to the idea of an interval estimate, but the concept of confidence level and calcualting formal confidence intervals would not be a part of what is expected in Algebra 2. Margin of error can be developed via simulation, building on the concept of sampling variability which is first introduced in grade 7.
While not an IC standard, S-ID.4 indicates that students would use calculators, spreadsheets and tables to estimate areas under a normal curve. If tables of the standard normal distribution are used to do this, students would need to use z-scores to move from an area under a particular normal distribution to an equvalent area for the standard normal distribution, so z-scores would probbly be covered there.