When someone says they are "going loco," it means they are going crazy or losing their mind. There are several other phrases that can be used to express the same sentiment. One common phrase is "losing it," which is often used when someone is feeling overwhelmed or experiencing intense emotions. Another synonym for "going loco" is "losing one's marbles," which is a playful way of describing someone who is becoming increasingly forgetful or absent-minded. Similarly, "cracking up" or "flipping out" can be used to describe someone who is experiencing a mental breakdown or losing control of their emotions.