Im a fluent Spanish speaker (I'm Hispanic). What my professor made me realize is that in order to speak Spanglish, you must be proficient at both languages in order to automatically switch languages in the same sentence. I grew up in a predominantly hispanic community. Many Hispanics grew up speaking Spanglish. Which is what a lot of Hispanic people are now using. Spanglish is not a language but a way of slang talking. As an LEO, you spend most of your times in the streets. Well that's where Spanglish is being used. It's not a formal language but a way of speaking that is widely used. We speak Spanish to our parents and elders, English with people who don't speak Spanish, and Spanglish with friends. I'm not sure if I'm doing a good job of explaining what I mean, but i feel that it's a modern way in which many hispanics now communicate.

TL;DR Spanglish is not a language but rather a modern way in which Hispanics communicate.