It is sound you would speak in English all the class. All or 95% of the class, I would say.
If you think some explaining will not be understood by your students, like a grammar point, keep on speaking in English but with more simple terms, and with examples, and by using the whiteboard.
Don’t shift to Spanish, don’t succumb to the temptation.
If you catch yourself speaking in Spanish, correct yourself aloud and continue, go on by speaking in English. Your students will understand more and more.
I’m not sure, but then, if you think they did not understand, you could use Spanish, what do you think please? / Photo from: soldier of the future. www infocusmagazine org. I would like that that kind of soldier, with that equipment, wouldn’t be necessary.