I have to agree with DCforMe's advice. First, make sure that your potential college choices even require SAT subject tests. (Many schools don't or make them optional, particularly if you are submitting ACT scores.) Remember that College Board doesn't allow you to pick and choose which test scores to send. So if you take ANY subject tests, they'll be sent along with your SAT reasoning test scores.
If you do decide to take subject tests, it sounds like you would probably do best with Math 2, Physics, and your first language.