Can I use straight bleach to sanitize with the nature 2 system or do I need to use mps and dichlor?

You shouldn't use straight bleach initially since you want to build up around 30 ppm CYA so should start out using Dichlor initially for around a week or so and then switch over to using bleach. See Using Chlorine in a Spa for more details. This is known as the Dichlor-then-bleach method, but does not need Nature2.

If you want to minimize the amount of chlorine (which I assume is why you got Nature2 in the first place), then you would use MPS with the Nature2 according to the Owner's Manual where the MPS is used before and after the soak to maintain a proper MPS level. You will probably still need to use Dichlor around once a week to keep the water clear.

How do you test for mps? Do I need to buy test strips?

I have potassium peroxymonosulfate 31.0% is this the same as MPS?

Yes it's the same.
I wouldn't use test strips for anything, The MPS will show up as combined chlorine in the standard DPD 3 test but you can buy specific test kits from Talylors, more on MPS and look at the testing at the bottom of the page.
http://www2.dupont.com/Oxone/en_US/assets/downloads/K20102%20Oxone%C2%AE%20Technical%20Bulletin.pdf

I have taylor k-2006 test kit. I now understand that I can test for mps like I would cc but how do I know when I need dichlor?

For every 10 ppm dichlor you add, you will also be adding 9 ppm CYA. So if you need 30 ppm CYA, you can add as much as 33 ppm FC as dichlor and be just fine. Once you have your CYA where you need it, switch to bleach.