Can I take CS 429 and another upper division CS course concurrently?

No. CS 429 provides the foundational material for upper division classes. Instead of taking upper division classes, students are asked to focus on their math requirements (calculus, M 340L, SSC 321, etc.) in this semester with CS 429. The only exception to this would be an FRI (CS 378) course. You would need to speak to the FRI department if you are not already involved in the FRI program to gain access to these courses.