I recommend everyone does Foundation Maths, it won't take you longer to complete your degree at all, because foundation maths gets counted as an elective, and all students have to do 4 electives by the end of their course anyway.
Also foundation maths is extremely easy, in the first lecture they taught us that 2 negatives makes a plus, ie. 2--2=4.
So if you want a guaranteed High Distinction for one of your electives (you might not ever get this chance again, once you've passed mm1 you can't do foundation maths), then do foundation maths, you don't even need to go to the lectures coz it's so easy, so you'll have more time to study for other harder subjects.
And then if you want to be a step ahead of every1 else, you can do mm1 in the summer holidays and get an extra subject out of your way, so you can have 1 semester down the track where you would only need to do 3 subjects, and have a bit of a bludge!
This is what I did because I only did 2 unit, and because foundation maths was so easy, I got motivated because of my high marks, and I started to enjoy maths so much that I got a high distinction for mm1.
That's what I did, think about that compared to some of my other friends who thought they would give mm1 a go and then they ended up failing it and having to pay $900 to repeat it, and then that also added 1 more semester to their degree.