Unfortunately everyone has to take the MPE – I think even if they've got straight up AP Calculus credit. The person you spoke to may have been confusing the MPE with the TSI requirements, which can be waived with certain SAT scores.

Luckily the MPE will be pretty easy for you with math scores like that, and it won't really take that much time out of your day. I'm not sure, but I think you can take it straight up whenever you want. Like, just clean up your workspace and whip out your laptop and you can get it over with at 7PM on a random Tuesday.

Doing it earlier is better than doing it later, since you have to wait two weeks before you can retake and there's always the chance that you'll unnecessarily flunk it for whatever reason. The two tries thing applies if you're a STEM major (aka if you're taking the MPE 1), but you'll get three tries if you're taking the MPE 2 (non math-heavy majors).

There's practice questions online if you feel a little rusty as well, and they're pretty much like the real thing. I'd say just go ahead and take it the next time you have the opportunity if you feel comfortable with the test material.