I am planning on taking either two Subject Tests (Math I and Math II) or retake the SAT in october. I intend to apply to an engineering school and want to do Math I and Math II to put on my resume, however my SAT is extremely low (1700s). Should I retake the SAT to get a higher score, or would it be better if I focus on doing well on Math I and Math II?
I would recommend going with the SAT - A raised SAT score can open a lot of doors.
However, if you decide to take Subject Tests instead, most colleges will want to see only 1 of the Math tests, not both. For engineering school, I suggest Math II and one of the science tests.
Agree with @1358531. Focus on your SAT, drop Math 1 and take Math 2 with either Biology/Chem or Physics.
Relatively few colleges use SAT subject tests, and most of those are selective enough that an SAT reasoning score of 1700 makes them unrealistic. So, unless you know that some realistic college on your list requires SAT subject tests, it is likely that a retry of the SAT reasoning or the ACT is a better use of time.
If you do take SAT subject tests, taking both math tests is not really useful (choose level 2 if you have had precalculus/trigonometry, level 1 otherwise). Colleges that want SAT subject tests vary in what they want (check their web sites), but they tend not to want two math tests.
Many engineers do better on the ACT. You might consider it.
The ACT may be better test for you.
I agree with above, take Math II and a Science Subject test.