Learning two programming languages at the same time is definitely not comparable to learning Spanish and Mandarin at the same time...those two languages are so different that you won't gain anything from it. Learning, say, Spanish and Italian at the same time might be a better analogy, since you'll start to see word roots and constructions that are shared among romance languages.

I think learning more than one programming language at the same time is a great way to help you tease out basic programming concepts from the vagaries in the syntax of an individual language. How to types work? Scopes? Functions? Loops? Arrays? Hash tables? Those are all things that, once you really grok as separate from, say, whitespace problems in Python or curly brace issues in C, allow you to much more easily read and eventually pick up other languages.