This was one of my favourite places to grab a bite to eat when I was in school. M4 is one of my go-to lunch and delivery spots, and never lets me down when I'm on one of my burrito bowl kicks.
There are a couple of locations in the city that I know of - both east and west. The restaurants seem to be relatively in order and clean, which is always a bonus. I personally love their burrito bowls. There are a ton of add-on options - both veggie and not - accommodating the majority of eaters and those with food restrictions. I personally always order a vegan bowl and I've never been disappointed. I've also heard good things about their burritos from friends (side note: there are always $5.00 burrito coupons flying around). The portions are massive and 100% worth the price. The service also tends to be quick and very friendly.
I recommend this establishment to anyone who is on the hunt for decent Mexican food!