I really want to get into a good mechanical engineering program, but I'm concerned because my Math score is only a 600 (lower than both my Reading and Writing scores). I've gotten As in all my math and science classes in high school, so there's no issue on that front. Should I reconsider my major because of my low math score? Is the math SAT score a make or break portion of a student's application for most engineering schools? I'm planning on retaking the test (I'm a junior), but I'm still worried, especially since the SAT is different now.
There are many colleges that will accept you into their engineering programs with a 600 on the math SAT. However, I would definitely encourage you to retake if you're typically a very strong math student and you feel your score doesn't reflect your abilities. If you didn't prepare much before the test, it might just come down to a lack of familiarity with the format and time constraints.
The Math section of the SAT is changing the least out of all the sections, so you can still use old test questions to prepare. The new version may even be easier for you, since they've tried to cut down on tricky and puzzle-like questions in favor of more direct questions that ask you to demonstrate specific math knowledge. You can review some new SAT practice tests here to get a sense of what this looks like.
You can even try taking an ACT practice test to see if you fare better than you did on the SAT. You might choose to switch to the ACT if it feels like an easier test for you.
Don't abandon your chosen major because of a standardized test score that was slightly lower than you expected. Keep working towards a higher score, and try to find schools that you like that match up with your stats.